Journal tags: pwas

34

sparkline

Web notifications on iOS

I’ve mentioned before that I don’t enable notifications on my phone. Text messages are the only exception. I don’t want to get notified if a new email arrives (I avoid email on my phone completely) and I certainly don’t want some social media app telling me somebody liked or faved something.

But the number one feature I’d like to see in Safari on iOS is web notifications.

It’s not for me personally, see. It’s because it’s the number one reason why people are choosing not to go all in progressive web apps.

Safari on iOS is the last holdout. But that equates to enough marketshare that many companies feel they can’t treat notifications as a progressive enhancement. While I may not agree with that decision myself, I get it.

When I’m evangelising the benefits of building on the open web instead of making separate iOS and Android apps, I inevitably get asked about notifications. As long as mobile Safari doesn’t support them—even though desktop Safari does—I’m somewhat stumped. There’s no polyfill for this feature other than building an entire native app, which is a bit extreme as polyfills go.

And of course, unlike on your Mac, you don’t have the option of using a different browser on your iPhone. As long as mobile Safari doesn’t support web notifications, nothing on iOS can support web notifications.

I’ve got progressive web apps on the home screen of my phone that match their native equivalents feature-for-feature. Twitter. Instagram. They’re really good. In some ways they’re superior to the native apps; the Twitter website is much calmer, and the Instagram website has no advertising. But if I wanted to get notifications from any of those sites, I’d have to keep the native apps installed just for that one feature.

So in the spirit of complaining about web browsers in a productive way, I just want to throw this plea out there: Apple, please support web notifications in mobile Safari!

The good news is that web notifications on iOS might be on their way. Huzzah!

Alas, we’re reliant on Maximiliano’s detective work to even get a glimpse of a future feature like this. Apple has no public roadmap for Safari. There’s this status page on the Webkit blog but it’s incomplete—web notifications don’t appear at all. In any case, WebKit and Safari aren’t the same thing. The only way of knowing if a feature might be implemented in Safari is if it shows up in Safari Technology Preview, at which point it’s already pretty far along.

So while my number one feature request for mobile Safari is web notifications, a close second would be a public roadmap.

It only seems fair. If Apple devrels are asking us developers what features we’d like to see implemented—as they should!—then shouldn’t those same developers also be treated with enough respect to share a roadmap with them? There’s not much point in us asking for features if, unbeknownst to us, that feature is already being worked on.

But, like I said, my number one request remains: web notifications on iOS …please!

A bug with progressive web apps on iOS

Dave recently wrote some good advice about what to do—and what not to do—when it comes to complaining about web browsers. I wrote something on this topic a little while back:

If there’s something about a web browser that you’re not happy with (or, indeed, if there’s something you’re really happy with), take the time to write it down and publish it

To summarise Dave’s advice, avoid conspiracy theories and snark; stick to specifics instead.

It’s very good advice that I should heed (especially the bit about avoiding snark). In that spirit, I’d like to document what I think is a bug on iOS.

I don’t need to name the specific browser, because there is basically only one browser allowed on iOS. That’s not snark; that’s a statement of fact.

This bug involves navigating from a progressive web app that has been installed on your home screen to an external web view.

To illustrate the bug, I’ll use the example of The Session. If you want to recreate the bug, you’ll need to have an account on The Session. Let me know if you want to set up a temporary account—I can take care of deleting it afterwards.

Here are the steps:

  1. Navigate to thesession.org in Safari on an iOS device.
  2. Add the site to your home screen.
  3. Open the installed site from your home screen—it will launch in standalone mode.
  4. Log in with your username and password.
  5. Using the site menu, navigate to the links section of the site.
  6. Click on any external link.
  7. After the external link opens in a web view, tap on “Done” to close the web view.

Expected behaviour: you are returned to the page you were on with no change of state.

Actual behaviour: you are returned to the page you were on but you are logged out.

So the act of visiting an external link in a web view while in a progressive web app in standalone mode seems to cause a loss of cookie-based authentication.

This isn’t permanent. Clicking on any internal link restores the logged-in state.

It is surprising though. My mental model for opening an external link in a web view is that it sits “above” the progressive web app, which remains in stasis “behind” it. But the page must actually be reloading, either when the web view is opened or when the web view is closed. And that reload is behaving like a fetch event without credentials.

Anyway, that’s my bug report. It may already be listed somewhere on the WebKit Bugzilla but I lack the deductive skills to find it. I’m not even sure if that’s the right place for this kind of bug. It might be specific to the operating system rather than the rendering engine.

This isn’t a high priority bug, but it is one of those cumulatively annoying software paper cuts.

Hope this helps!

Screenshots

I wrote about how I created a page on The Session with instructions for installing the site to your home screen. When I said that I included screenshots on that page, I may have underplayed the effort involved. It was real faff.

I’ve got an iPhone so generating screenshots (and video) from that wasn’t too bad. But I don’t have access to an Android phone. I found myself scouring the web for templates that I could use to mockup a screenshot of the address bar.

That got me thinking…

Wouldn’t it be cool if there were a service that generated those screenshots for you? You give it a URL, and it spits out screenshots of the site complete with overlays showing the installation flow on Android and iOS. It could even generate the img markup, complete with differently-scaled images for the srcset attribute.

Download the images. Copy that markup. Paste it into a page on your site. Boom! Now you’ve got somewhere to point your visitors to if you’d like them to install your progressive web app.

There are already some services out there for generating screenshots of mobile phones but they’re missing is the menu overlays for adding to home screen.

The devrels at both Google and Microsoft have been doing a great job of promoting progressive web apps. They’ve built tools to help you with tasks like generating icons or creating your web app manifest. It would be sooooo nifty if those tools also generated instructional screenshots for adding to home screen!

Installing progressive web apps

I don’t know about you, but it seems like everyone I follow on Twitter is playing Wordle. Although I don’t play the game myself, I think it’s pretty great.

Not only does Wordle have a very sweet backstory, but it’s also unashamedly on the web. If you want to play, you go to the URL powerlanguage.co.uk/wordle. That’s it. No need to download an app.

That hasn’t stopped some nefarious developers trying to trick people into downloading their clones of Wordle from app stores. App stores, which are meant to be curated and safe, are in fact filled with dodgy knock-offs and scams. Contrary to popular belief, the web is quite literally a safer bet.

Wordle has a web app manifest, which means you can add it to your home screen and it will behave just like a native app (although I don’t believe it has offline support). That’s great, but the process of adding a web app to your home screen on iOS is ludicrously long-winded.

Macworld published an article detailing how to get the real Wordle app on your iPhone or iPad. On the one hand it’s great to see this knowledge being spread. On the other hand it’s dispiriting that it’s even necessary to tell people that they can do this, like it’s a hidden nerdy secret just for power users.

At this point I’ve pretty much given up on Apple ever doing anything about this pathetic situation. So what can I do instead?

Well, taking my cue from that Macworld article, the least I can do is inform people how they can add a progressive web app to their home screen.

That’s what I’ve done on thesession.org. I’ve published a page on how to install The Session to your home screen.

On both Android and iPhone the journey to installing a progressive web app begins with incomprehensible iconography. On Android you must first tap on the unlabeled kebab icon—three vertical dots. On iOS you must first tap on the unlabeled share icon—a square with an arrow coming out of it.

The menu icon on Android. The share icon on iOS.

When it comes to mobile operating systems, consumer choice means you choose which kind of mystery meat to eat.

I’ve included screenshots to help people identify these mysterious portals. For iOS I’ve also included a video to illustrate the quest to find the secret menu item buried beneath the share icon.

I’ve linked to the page with the installation instructions from the site’s “help” page and the home page.

Handy tip: when you’re adding a start_url value to your web app manifest, it’s common to include a query string like this:

start_url: "/?homescreen"

I’m guessing most people to that so they can get analytics on how many people are starting from an icon tap. I don’t do analytics on The Session but I’m still using that query string in my start_url. On the home page of the site, I check for the existence of the query string. If it exists, I don’t show the link to the installation page. So once someone has installed the site to their home screen, they shouldn’t see that message when they launch The Session.

If you’ve got a progressive web app, it might be worth making a page with installation instructions rather than relying on browsers to proactively inform your site’s visitors. You’d still need to figure out the right time and place to point people to that page, but at least the design challenge would be in your hands.

Should you decide to take a leaf out of the Android and iOS playbooks and use mystery meat navigation to link to such a page, there’s an emoji you could potentially use: 📲

It’s still worse than using actual words, but it might be better than some random combination of dots, squares and arrows.

(I’m not really serious about using that emoji, but if you do, be sure to use a sensible aria-label value on the enclosing a element.)

Media queries with display-mode

It’s said that the best way to learn about something is to teach it. I certainly found that to be true when I was writing the web.dev course on responsive design.

I felt fairly confident about some of the topics, but I felt somewhat out of my depth when it came to some of the newer modern additions to browsers. The last few modules in particular were unexplored areas for me, with topics like screen configurations and media features. I learned a lot about those topics by writing about them.

Best of all, I got to put my new-found knowledge to use! Here’s how…

The Session is a progressive web app. If you add it to the home screen of your mobile device, then when you launch the site by tapping on its icon, it behaves just like a native app.

In the web app manifest file for The Session, the display-mode property is set to “standalone.” That means it will launch without any browser chrome: no address bar and no back button. It’s up to me to provide the functionality that the browser usually takes care of.

So I added a back button in the navigation interface. It only appears on small screens.

Do you see the assumption I made?

I figured that the back button was most necessary in the situation where the site had been added to the home screen. That only happens on mobile devices, right?

Nope. If you’re using Chrome or Edge on a desktop device, you will be actively encourged to “install” The Session. If you do that, then just as on mobile, the site will behave like a standalone native app and launch without any browser chrome.

So desktop users who install the progressive web app don’t get any back button (because in my CSS I declare that the back button in the interface should only appear on small screens).

I was alerted to this issue on The Session:

It downloaded for me but there’s a bug, Jeremy - there doesn’t seem to be a way to go back.

Luckily, this happened as I was writing the module on media features. I knew exactly how to solve this problem because now I knew about the existence of the display-mode media feature. It allows you to write media queries that match the possible values of display-mode in a web app manifest:

.goback {
  display: none;
}
@media (display-mode: standalone) {
  .goback {
    display: inline;
  }
}

Now the back button shows up if you “install” The Session, regardless of whether that’s on mobile or desktop.

Previously I made the mistake of inferring whether or not to show the back button based on screen size. But the display-mode media feature allowed me to test the actual condition I cared about: is this user navigating in standalone mode?

If I hadn’t been writing about media features, I don’t think I would’ve been able to solve the problem. It’s a really good feeling when you’ve just learned something new, and then you immediately find exactly the right use case for it!

Safari 15

If you download Safari Technology Preview you can test drive features that are on their way in Safari 15. One of those features, announced at Apple’s World Wide Developer Conference, is coloured browser chrome via support for the meta value of “theme-color.” Chrome on Android has supported this for a while but I believe Safari is the first desktop browser to add support. They’ve also added support for the media attribute on that meta element to handle “prefers-color-scheme.”

This is all very welcome, although it does remind me a bit of when Internet Explorer came out with the ability to make coloured scrollbars. I mean, they’re nice features’n’all, but maybe not the most pressing? Safari is still refusing to acknowledge progressive web apps.

That’s not quite true. In her WWDC video Jen demonstrates how you can add a progressive web app like Resilient Web Design to your home screen. I’m chuffed that my little web book made an appearance, but when you see how you add a site to your home screen in iOS, it’s somewhat depressing.

The steps to add a website to your home screen are:

  1. Tap the “share” icon. It’s not labelled “share.” It’s a square with an arrow coming out of the top of it.
  2. A drawer pops up. The option to “add to home screen” is nowhere to be seen. You have to pull the drawer up further to see the hidden options.
  3. Now you must find “add to home screen” in the list
  • Copy
  • Add to Reading List
  • Add Bookmark
  • Add to Favourites
  • Find on Page
  • Add to Home Screen
  • Markup
  • Print

It reminds of this exchange in The Hitchhiker’s Guide To The Galaxy:

“You hadn’t exactly gone out of your way to call attention to them had you? I mean like actually telling anyone or anything.”

“But the plans were on display…”

“On display? I eventually had to go down to the cellar to find them.”

“That’s the display department.”

“With a torch.”

“Ah, well the lights had probably gone.”

“So had the stairs.”

“But look you found the notice didn’t you?”

“Yes,” said Arthur, “yes I did. It was on display in the bottom of a locked filing cabinet stuck in a disused lavatory with a sign on the door saying ‘Beware of The Leopard.’”

Safari’s current “support” for adding progressive web apps to the home screen feels like the minimum possible …just enough to use it as a legal argument if you happen to be litigated against for having a monopoly on app distribution. “Hey, you can always make a web app!” It’s true in theory. In practice it’s …suboptimal, to put it mildly.

Still, those coloured tab bars are very nice.

It’s a little bit weird that this stylistic information is handled by HTML rather than CSS. It’s similar to the meta viewport value in that sense. I always that the plan was to migrate that to CSS at some point, but here we are a decade later and it’s still very much part of our boilerplate markup.

Some people have remarked that the coloured browser chrome can make the URL bar look like part of the site so people might expect it to operate like a site-specific search.

I also wonder if it might blur “the line of death”; that point in the UI where the browser chrome ends and the website begins. Does the unified colour make it easier to spoof browser UI?

Probably not. You can already kind of spoof browser UI by using the right shade of grey. Although the removal any kind of actual line in Safari does give me pause for thought.

I tend not to think of security implications like this by default. My first thought tends to be more about how I can use the feature. It’s only after a while that I think about how bad actors might abuse the same feature. I should probably try to narrow the gap between those thoughts.

Service worker weirdness in Chrome

I think I’ve found some more strange service worker behaviour in Chrome.

It all started when I was checking out the very nice new redesign of WebPageTest. I figured while I was there, I’d run some of my sites through it. I passed in a URL from The Session. When the test finished, I noticed that the “screenshot” tab said that something was being logged to the console. That’s odd! And the file doing the logging was the service worker script.

I fired up Chrome (which isn’t my usual browser), and started navigating around The Session with dev tools open to see what appeared in the console. Sure enough, there was a failed fetch attempt being logged. The only time my service worker script logs anything is in the catch clause of fetching pages from the network. So Chrome was trying to fetch a web page, failing, and logging this error:

The service worker navigation preload request failed with a network error.

But all my pages were loading just fine. So where was the error coming from?

After a lot of spelunking and debugging, I think I’ve figured out what’s happening…

First of all, I’m making use of navigation preloads in my service worker. That’s all fine.

Secondly, the website is a progressive web app. It has a manifest file that specifies some metadata, including start_url. If someone adds the site to their home screen, this is the URL that will open.

Thirdly, Google recently announced that they’re tightening up the criteria for displaying install prompts for progressive web apps. If there’s no network connection, the site still needs to return a 200 OK response: either a cached copy of the URL or a custom offline page.

So here’s what I think is happening. When I navigate to a page on the site in Chrome, the service worker handles the navigation just fine. It also parses the manifest file I’ve linked to and checks to see if that start URL would load if there were no network connection. And that’s when the error gets logged.

I only noticed this behaviour because I had specified a query string on my start URL in the manifest file. Instead of a start_url value of /, I’ve set a start_url value of /?homescreen. And when the error shows up in the console, the URL being fetched is /?homescreen.

Crucially, I’m not seeing a warning in the console saying “Site cannot be installed: Page does not work offline.” So I think this is all fine. If I were actually offline, there would indeed be an error logged to the console and that start_url request would respond with my custom offline page. It’s just a bit confusing that the error is being logged when I’m online.

I thought I’d share this just in case anyone else is logging errors to the console in the catch clause of fetches and is seeing an error even when everything appears to be working fine. I think there’s nothing to worry about.

Update: Jake confirmed my diagnosis and agreed that the error is a bit confusing. The good news is that it’s changing. In Chrome Canary the error message has already been updated to:

DOMException: The service worker navigation preload request failed due to a network error. This may have been an actual network error, or caused by the browser simulating offline to see if the page works offline: see https://w3c.github.io/manifest/#installability-signals

Much better!

Future Sync 2020

I was supposed to be in Plymouth yesterday, giving the opening talk at this year’s Future Sync conference. Obviously, that train journey never happened, but the conference did.

The organisers gave us speakers the option of pre-recording our talks, which I jumped on. It meant that I wouldn’t be reliant on a good internet connection at the crucial moment. It also meant that I was available to provide additional context—mostly in the form of a deluge of hyperlinks—in the chat window that accompanied the livestream.

The whole thing went very smoothly indeed. Here’s the video of my talk. It was The Layers Of The Web, which I’ve only given once before, at Beyond Tellerrand Berlin last November (in the Before Times).

As well as answering questions in the chat room, people were also asking questions in Sli.do. But rather than answering those questions there, I was supposed to respond in a social medium of my choosing. I chose my own website, with copies syndicated to Twitter.

Here are those questions and answers…

The first few questions were about last years’s CERN project, which opens the talk:

Based on what you now know from the CERN 2019 WorldWideWeb Rebuild project—what would you have done differently if you had been part of the original 1989 Team?

I responded:

Actually, I think the original WWW project got things mostly right. If anything, I’d correct what came later: cookies and JavaScript—those two technologies (which didn’t exist on the web originally) are the source of tracking & surveillance.

The one thing I wish had been done differently is I wish that JavaScript were a same-origin technology from day one:

https://adactio.com/journal/16099

Next question:

How excited were you when you initially got the call for such an amazing project?

My predictable response:

It was an unbelievable privilege! I was so excited the whole time—I still can hardly believe it really happened!

https://adactio.com/journal/14803

https://adactio.com/journal/14821

Later in the presentation, I talked about service workers and progressive web apps. I got a technical question about that:

Is there a limit to the amount of local storage a PWA can use?

I answered:

Great question! Yes, there are limits, but we’re generally talking megabytes here. It varies from browser to browser and depends on the available space on the device.

But files stored using the Cache API are less likely to be deleted than files stored in the browser cache.

More worrying is the announcement from Apple to only store files for a week of browser use:

https://adactio.com/journal/16619

Finally, there was a question about the over-arching theme of the talk…

Great talk, Jeremy. Do you encounter push-back when using the term “Progressive Enhancement”?

My response:

Yes! …And that’s why I never once used the phrase “progressive enhancement” in my talk. 🙂

There’s a lot of misunderstanding of the term. Rather than correct it, I now avoid it:

https://adactio.com/journal/9195

Instead of using the phrase “progressive enhancement”, I now talk about the benefits and effects of the technique: resilience, universality, etc.

Future Sync Distributed 2020

Apple’s attack on service workers

Apple aren’t the best at developer relations. But, bad as their communications can be, I’m willing to cut them some slack. After all, they’re not used to talking with the developer community.

John Wilander wrote a blog post that starts with some excellent news: Full Third-Party Cookie Blocking and More. Safari is catching up to Firefox and disabling third-party cookies by default. Wonderful! I’ve had third-party cookies disabled for a few years now, and while something occassionally breaks, it’s honestly a pretty great experience all around. Denying companies the ability to track users across sites is A Good Thing.

In the same blog post, John said that client-side cookies will be capped to a seven-day lifespan, as previously announced. Just to be clear, this only applies to client-side cookies. If you’re setting a cookie on the server, using PHP or some other server-side language, it won’t be affected. So persistent logins are still doable.

Then, in an audacious example of burying the lede, towards the end of the blog post, John announces that a whole bunch of other client-side storage technologies will also be capped to seven days. Most of the technologies are APIs that, like cookies, can be used to store data: Indexed DB, Local Storage, and Session Storage (though there’s no mention of the Cache API). At the bottom of the list is this:

Service Worker registrations

Okay, let’s clear up a few things here (because they have been so poorly communicated in the blog post)…

The seven day timer refers to seven days of Safari usage, not seven calendar days (although, given how often most people use their phones, the two are probably interchangable). So if someone returns to your site within a seven day period of using Safari, the timer resets to zero, and your service worker gets a stay of execution. Lucky you.

This only applies to Safari. So if your site has been added to the home screen and your web app manifest has a value for the “display” property like “standalone” or “full screen”, the seven day timer doesn’t apply.

That piece of information was missing from the initial blog post. Since the blog post was updated to include this clarification, some people have taken this to mean that progressive web apps aren’t affected by the upcoming change. Not true. Only progressive web apps that have been added to the home screen (and that have an appropriate “display” value) will be spared. That’s a vanishingly small percentage of progressive web apps, especially on iOS. To add a site to the home screen on iOS, you need to dig and scroll through the share menu to find the right option. And you need to do this unprompted. There is no ambient badging in Safari to indicate that a site is installable. Chrome’s install banner isn’t perfect, but it’s better than nothing.

Just a reminder: a progressive web app is a website that

  • runs on HTTPS,
  • has a service worker,
  • and a web manifest.

Adding to the home screen is something you can do with a progressive web app (or any other website). It is not what defines progressive web apps.

In any case, this move to delete service workers after seven days of using Safari is very odd, and I’m struggling to find the connection to the rest of the blog post, which is about technologies that can store data.

As I understand it, with the crackdown on setting third-party cookies, trackers are moving to first-party technologies. So whereas in the past, a tracking company could tell its customers “Add this script element to your pages”, now they have to say “Add this script element and this script file to your pages.” That JavaScript file can then store a unique idenitifer on the client. This could be done with a cookie, with Local Storage, or with Indexed DB, for example. But I’m struggling to understand how a service worker script could be used in this way. I’d really like to see some examples of this actually happening.

The best explanation I can come up with for this move by Apple is that it feels like the neatest solution. That’s neat as in tidy, not as in nifty. It is definitely not a nifty solution.

If some technologies set by a specific domain are being purged after seven days, then the tidy thing to do is purge all technologies from that domain. Service workers are getting included in that dragnet.

Now, to be fair, browsers and operating systems are free to clean up storage space as they see fit. Caches, Local Storage, Indexed DB—all of those are subject to eventually getting cleaned up.

So I was curious. Wanting to give Apple the benefit of the doubt, I set about trying to find out how long service worker registrations currently last before getting deleted. Maybe this announcement of a seven day time limit would turn out to be not such a big change from current behaviour. Maybe currently service workers last for 90 days, or 60, or just 30.

Nope:

There was no time limit previously.

This is not a minor change. This is a crippling attack on service workers, a technology specifically designed to improve the user experience for return visits, whether it’s through improved performance or offline access.

I wouldn’t be so stunned had this announcement come with an accompanying feature that would allow Safari users to know when a website is a progressive web app that can be added to the home screen. But Safari continues to ignore the existence of progressive web apps. And now it will actively discourage people from using service workers.

If you’d like to give feedback on this ludicrous development, you can file a bug (down in the cellar in the bottom of a locked filing cabinet stuck in a disused lavatory with a sign on the door saying “Beware of the Leopard”).

No doubt there will still be plenty of Apple apologists telling us why it’s good that Safari has wished service workers into the cornfield. But make no mistake. This is a terrible move by Apple.

I will say this though: given The Situation we’re all living in right now, some good ol’ fashioned Hot Drama by a browser vendor behaving badly feels almost comforting.

Install prompt

There’s an interesting thread on Github about the tongue-twistingly named beforeinstallpromt JavaScript event.

Let me back up…

Progressive web apps. You know what they are, right? They’re websites that have taken their vitamins. Specifically, they’re responsive websites that:

  1. are served over HTTPS,
  2. have a web app manifest, and
  3. have a service worker handling the offline scenario.

The web app manifest—a JSON file of metadata—is particularly useful for describing how your site should behave if someone adds it to their home screen. You can specify what icon should be used. You can specify whether the site should launch in a browser or as a standalone app (practically indistinguishable from a native app). You can specify which URL on the site should be used as the starting point when the site is launched from the home screen.

So progressive web apps work just fine when you visit them in a browser, but they really shine when you add them to your home screen. It seems like pretty much everyone is in agreement that adding a progressive web app to your home screen shouldn’t be an onerous task. But how does the browser let the user know that it might be a good idea to “install” the web site they’re looking at?

The Samsung Internet browser does ambient badging—a + symbol shows up to indicate that a website can be installed. This is a great approach!

I hope that Chrome on Android will also use ambient badging at some point. To start with though, Chrome notified users that a site was installable by popping up a notification at the bottom of the screen. I think these might be called “toasts”.

Getting the “add to home screen” prompt for https://huffduffer.com/ on Android Chrome. And there’s the “add to home screen” prompt for https://html5forwebdesigners.com/ HTTPS + manifest.json + Service Worker = “Add to Home Screen” prompt. Add to home screen.

Needless to say, the toast notification wasn’t very effective. That’s because we web designers and developers have spent years teaching people to immediately dismiss those notifications without even reading them. Accept our cookies! Sign up to our newsletter! Install our native app! Just about anything that’s user-hostile gets put in a notification (either a toast or an overlay) and shoved straight in the user’s face before they’ve even had time to start reading the content they came for in the first place. Users will then either:

  1. turn around and leave, or
  2. use muscle memory reach for that X in the corner of the notification.

A tiny fraction of users might actually click on the call to action, possibly by mistake.

Chrome didn’t abandon the toast notification for progressive web apps, but it did change when they would appear. Rather than the browser deciding when to show the prompt—usually when the user has just arrived on the site—a new JavaScript event called beforeinstallprompt can be used.

It’s a bit weird though. You have to “capture” the event that fires when the prompt would have normally been shown, subdue it, hold on to that event, and then re-release it when you think it should be shown (like when the user has completed a transaction, for example, and having your site on the home screen would genuinely be useful). That’s a lot of hoops. Here’s the code I use on The Session to only show the installation prompt to users who are logged in.

The end result is that the user is still shown a toast notification, but at least this time it’s the site owner who has decided when it will be shown. The Chrome team call this notification “the mini-info bar”, and Pete acknowledges that it’s not ideal:

The mini-infobar is an interim experience for Chrome on Android as we work towards creating a consistent experience across all platforms that includes an install button into the omnibox.

I think “an install button in the omnibox” means ambient badging in the browser interface, which would be great!

Anyway, back to that thread on Github. Basically, neither Apple nor Mozilla are going to implement the beforeinstallprompt event (well, technically Mozilla have implemented it but they’re not going to ship it). That’s fair enough. It’s an interim solution that’s not ideal for all reasons I’ve already covered.

But there’s a lot of pushback. Even if the details of beforeinstallprompt are troublesome, surely there should be some way for site owners to let users know that can—or should—install a progressive web app? As a site owner, I have a lot of sympathy for that viewpoint. But I also understand the security and usability issues that can arise from bad actors abusing this mechanism.

Still, I have to hand it to Chrome: even if we put the beforeinstallprompt event to one side, the browser still has a mechanism for letting users know that a progressive web app can be installed—the mini info bar. It’s not a great mechanism, but it’s better than nothing. Nothing is precisely what Firefox and Safari currently offer (though Firefox is experimenting with something).

In the case of Safari, not only do they not provide a mechanism for letting the user know that a site can be installed, but since the last iOS update, they’ve buried the “add to home screen” option even deeper in the “sharing sheet” (the list of options that comes up when you press the incomprehensible rectangle-with-arrow-emerging-from-it icon). You now have to scroll below the fold just to find the “add to home screen” option.

So while I totally get the misgivings about beforeinstallprompt, I feel that a constructive alternative wouldn’t go amiss.

And that’s all I have to say about that.

Except… there’s another interesting angle to that Github thread. There’s talk of allowing sites that are launched from the home screen to have access to more features than a site inside a web browser. Usually permissions on the web are explicitly granted or denied on a case-by-case basis: geolocation; notifications; camera access, etc. I think this is the first time I’ve heard of one action—adding to the home screen—being used as a proxy for implicitly granting more access. Very interesting. Although that idea seems to be roundly rejected here:

A key argument for using installation in this manner is that some APIs are simply so powerful that the drive-by web should not be able to ask for them. However, this document takes the position that installation alone as a restriction is undesirable.

Then again:

I understand that Chromium or Google may hold such a position but Apple’s WebKit team may not necessarily agree with such a position.

The Web Share API in Safari on iOS

I implemented the Web Share API over on The Session back when it was first available in Chrome in Android. It’s a nifty and quite straightforward API that allows websites to make use of the “sharing drawer” that mobile operating systems provide from within a web browser.

I already had sharing buttons that popped open links to Twitter, Facebook, and email. You can see these sharing buttons on individual pages for tunes, recordings, sessions, and so on.

I was already intercepting clicks on those buttons. I didn’t have to add too much to also check for support for the Web Share API and trigger that instead:

if (navigator.share) {
  navigator.share(
    {
      title: document.querySelector('title').textContent,
      text: document.querySelector('meta[name="description"]').getAttribute('content'),
      url: document.querySelector('link[rel="canonical"]').getAttribute('href')
    }
  );
}

That worked a treat. As you can see, there are three fields you can pass to the share() method: title, text, and url. You don’t have to provide all three.

Earlier this year, Safari on iOS shipped support for the Web Share API. I didn’t need to do anything. ‘Cause that’s how standards work. You can make use of APIs before every browser supports them, and then your website gets better and better as more and more browsers add support.

But I recently discovered something interesting about the iOS implementation.

When the share() method is triggered, iOS provides multiple ways of sharing: Messages, Airdrop, email, and so on. But the simplest option is the one labelled “copy”, which copies to the clipboard.

Here’s the thing: if you’ve provided a text parameter to the share() method then that’s what’s going to get copied to the clipboard—not the URL.

That’s a shame. Personally, I think the url field should take precedence. But I don’t think this is a bug, per se. There’s nothing in the spec to say how operating systems should handle the data sent via the Web Share API. Still, I think it’s a bit counterintuitive. If I’m looking at a web page, and I opt to share it, then surely the URL is the most important piece of data?

I’m not even sure where to direct this feedback. I guess it’s under the purview of the Safari team, but it also touches on OS-level interactions. Either way, I hope that somebody at Apple will consider changing the current behaviour for copying Web Share data to the clipboard.

In the meantime, I’ve decided to update my code to remove the text parameter:

if (navigator.share) {
  navigator.share(
    {
      title: document.querySelector('title').textContent,
      url: document.querySelector('link[rel="canonical"]').getAttribute('href')
    }
  );
}

If the behaviour of Safari on iOS changes, I’ll reinstate the missing field.

By the way, if you’re making progressive web apps that have display: standalone in the web app manifest, please consider using the Web Share API. When you remove the browser chrome, you’re removing the ability for users to easily share URLs. The Web Share API gives you a way to reinstate that functionality.

Ch-ch-ch-changes

It’s browser updatin’ time! Firefox 65 just dropped. So did Chrome 72. Safari 12.1 is shipping with iOS 12.2.

It’s interesting to compare the release notes for each browser and see the different priorities reflected in them (this is another reason why browser diversity is A Good Thing).

A lot of the Firefox changes are updates to dev tools; they just keep getting better and better. In fact, I’m not sure “dev tools” is the right word for them. With their focus on layout, typography, and accessibility, “design tools” might be a better term.

Oh, and Firefox is shipping support for some CSS properties that really help with print style sheets, so I’m disproportionately pleased about that.

In Safari’s changes, I’m pleased to see that the datalist element is finally getting implemented. I’ve been a fan of that element for many years now. (Am I a dork for having favourite HTML elements? Or am I a dork for even having to ask that question?)

And, of course, it wouldn’t be a Safari release without a new made up meta tag. From the people who brought you such hits as viewport and apple-mobile-web-app-capable, comes …supported-color-schemes (Apple likes to make up meta tags almost as much as Google likes to make up rel values).

There’ll be a whole bunch of improvements in how progressive web apps will behave once they’ve been added to the home screen. We’ll finally get some state persistence if you navigate away from the window!

Updated the behavior of websites saved to the home screen on iOS to pause in the background instead of relaunching each time.

Maximiliano Firtman has a detailed list of the good, the bad, and the “not sure yet if good” for progressive web apps on iOS 12.2 beta. Thomas Steiner has also written up the progress of progressive web apps in iOS 12.2 beta. Both are published on Ev’s blog.

At first glance, the release notes for Chrome 72 are somewhat paltry. The big news doesn’t even seem to be listed there. Maximiliano Firtman again:

Chrome 72 for Android shipped the long-awaited Trusted Web Activity feature, which means we can now distribute PWAs in the Google Play Store!

Very interesting indeed! I’m not sure if I’m ready to face the Kafkaesque process of trying to add something to the Google Play Store just yet, but it’s great to know that I can. Combined with the improvements coming in iOS 12.2, these are exciting times for progressive web apps!

Greater expectations

I got an intriguing email recently from someone who’s a member of The Session, the community website about Irish traditional music that I run. They said:

When I recently joined, I used my tablet to join. Somewhere I was able to download The Session app onto my tablet.

But there is no native app for The Session. Although, as it’s a site that I built, it is, a of course, progressive web app.

They went on to say:

I wanted to put the app on my phone but I can’t find the app to download it. Can I have the app on more than one device? If so, where is it available?

I replied saying that yes, you can absolutely have it on more than one device:

But you don’t find The Session app in the app store. Instead you go to the website https://thesession.org and then add it to your home screen from your browser.

My guess is that this person had added The Session to the home screen of their Android tablet, probably following the “add to home screen” prompt. I recently added some code to use the window.beforeinstallprompt event so that the “add to home screen” prompt would only be shown to visitors who sign up or log in to The Session—a good indicator of engagement, I reckon, and it should reduce the chance of the prompt being dismissed out of hand.

So this person added The Session to their home screen—probably as a result of being prompted—and then used it just like any other app. At some point, they didn’t even remember how the app got installed:

Success! I did it. Thanks. My problem was I was looking for an app to download.

On the one hand, this is kind of great: here’s an example where, in the user’s mind, there’s literally no difference between the experience of using a progressive web app and using a native app. Win!

But on the other hand, the expectation is still that apps are to be found in an app store, not on the web. This expectation is something I wrote about recently (and Justin wrote a response to that post). I finished by saying:

Perhaps the inertia we think we’re battling against isn’t such a problem as long as we give people a fast, reliable, engaging experience.

When this member of The Session said “My problem was I was looking for an app to download”, I responded by saying:

Well, I take that as a compliment—the fact that once the site is added to your home screen, it feels just like a native app. :-)

And they said:

Yes, it does!

Altering expectations

Luke has written up the selection process he went through when Clearleft was designing the Virgin Holidays app. When it comes to deploying on mobile, there were three options:

  1. Native apps
  2. A progressive web app
  3. A hybrid app

The Virgin Holidays team went with that third option.

Now, it will come as no surprise that I’m a big fan of the second option: building a progressive web app (or turning an existing site into a progressive web app). I think a progressive web app is a great solution for travel apps, and the use-case that Luke describes sounds perfect:

Easy access to resort staff and holiday details that could be viewed offline to help as many customers as possible travel without stress and enjoy a fantastic holiday

Luke explains why they choice not to go with a progressive web app.

The current level of support and leap in understanding meant we’d risk alienating many of our customers.

The issue of support is one that is largely fixed at this point. When Clearleft was working on the Virgin Holidays app, service workers hadn’t landed in iOS. Hence, the risk of alienating a lot of customers. But now that Mobile Safari has offline capabilities, that’s no longer a problem.

But it’s the second reason that’s trickier:

Simply put, customers already expected to find us in the App Store and are familiar with what apps can historically offer over websites.

I think this is the biggest challenge facing progressive web apps: battling expectations.

For over a decade, people have formed ideas about what to expect from the web and what to expect from native. From a technical perspective, native and web have become closer and closer in capabilities. But people’s expectations move slower than technological changes.

First of all, there’s the whole issue of discovery: will people understand that they can “install” a website and expect it to behave exactly like a native app? This is where install prompts and ambient badging come in. I think ambient badging is the way to go, but it’s still a tricky concept to explain to people.

But there’s another way of looking at the current situation. Instead of seeing people’s expectations as a negative factor, maybe it’s an opportunity. There’s an opportunity right now for companies to be as groundbreaking and trendsetting as Wired.com when it switched to CSS for layout, or The Boston Globe when it launched its responsive site.

It makes for a great story. Just look at the Pinterest progressive web app for an example (skip to the end to get to the numbers):

Weekly active users on mobile web have increased 103 percent year-over-year overall, with a 156 percent increase in Brazil and 312 percent increase in India. On the engagement side, session length increased by 296 percent, the number of Pins seen increased by 401 percent and people were 295 percent more likely to save a Pin to a board. Those are amazing in and of themselves, but the growth front is where things really shined. Logins increased by 370 percent and new signups increased by 843 percent year-over-year. Since we shipped the new experience, mobile web has become the top platform for new signups. And for fun, in less than 6 months since fully shipping, we already have 800 thousand weekly users using our PWA like a native app (from their homescreen).

Now admittedly their previous mobile web experience was a dreadful doorslam, but still, those are some amazing statistics!

Maybe we’re underestimating the malleability of people’s expectations when it comes to the web on mobile. Perhaps the inertia we think we’re battling against isn’t such a problem as long as we give people a fast, reliable, engaging experience.

If you build that, they will come.

Twitter and Instagram progressive web apps

Since support for service workers landed in Mobile Safari on iOS, I’ve been trying a little experiment. Can I replace some of the native apps I use with progressive web apps?

The two major candidates are Twitter and Instagram. I added them to my home screen, and banished the native apps off to a separate screen. I’ve been using both progressive web apps for a few months now, and I have to say, they’re pretty darn great.

There are a few limitations compared to the native apps. On Twitter, if you follow a link from a tweet, it pops open in Safari, which is fine, but when you return to Twitter, it loads anew. This isn’t any fault of Twitter—this is the way that web apps have worked on iOS ever since they introduced their weird web-app-capable meta element. I hope this behaviour will be fixed in a future update.

Also, until we get web notifications on iOS, I need to keep the Twitter native app around if I want to be notified of a direct message (the only notification I allow).

Apart from those two little issues though, Twitter Lite is on par with the native app.

Instagram is also pretty great. It too suffers from some navigation issues. If I click through to someone’s profile, and then return to the main feed, it also loads it anew, losing my place. It would be great if this could be fixed.

For some reason, the Instagram web app doesn’t allow uploading multiple photos …which is weird, because I can upload multiple photos on my own site by adding the multiple attribute to the input type="file" in my posting interface.

Apart from that, though, it works great. And as I never wanted notifications from Instagram anyway, the lack of web notifications doesn’t bother me at all. In fact, because the progressive web app doesn’t keep nagging me about enabling notifications, it’s a more pleasant experience overall.

Something else that was really annoying with the native app was the preponderance of advertisements. It was really getting out of hand.

Well …(looks around to make sure no one is listening)… don’t tell anyone, but the Instagram progressive web app—i.e. the website—doesn’t have any ads at all!

Here’s hoping it stays that way.

Clearleft.com is a progressive web app

What’s that old saying? The cobbler’s children have no shoes that work offline. Or something.

It’s been over a year since the Clearleft site relaunched and I listed some of the next steps I had planned:

Service worker. It’s a no-brainer. Now that the Clearleft site is (finally!) running on HTTPS, having a simple service worker to cache static assets like CSS, JavaScript and some images seems like the obvious next step.

You know how it is. Those no-brainer tasks are exactly the kind of thing that end up on a to-do list without ever quite getting to-done. Meanwhile I’ve been writing and speaking about how any website can be a progressive web app. I think Alanis Morissette used to sing about this sort of situation.

Enough is enough! Clearleft.com is now a progressive web app. It has a manifest file and a service worker script.

The service worker logic is fairly straightforward, and taken almost verbatim from Going Offline. As you navigate around the site, the service worker applies different logic depending on the kind of file you’re requesting:

  • Pages are served fresh from the network, falling back to the cache when there’s a problem.
  • Everything else is served from the cache where possible, resorting to the network only if there’s no match in the cache—quite the performance boost!

In both cases, if a page or a file is retrieved from the network, it’s gets put into a cache. I’ve got one cache for pages, and another for everything else. And even if a file is retrieved from that cache, I still fire off a fetch request to grab a fresh copy for the cache. So while there’s a chance that a stale file might be served up, it will only ever be slightly stale, and the next time it’s requested, it’ll be fresh.

In the worst-case scenario, when a page can’t be retrieved from the network or the cache, you end up seeing a custom offline page. There you can see a list of any pages that are cached (meaning you can revisit them even without an internet connection).

A custom offline page showing a list of URLs.

It’s not ideal—page titles would be friendlier than URLs—but it’s a start. I’m sure I’ll revisit it soon. Honest.

Oh, and after a year of procrastinating about doing this, guess how long it took? About half a day. Admittedly, this isn’t my first progressive web app, and the more you build ‘em, the easier it gets. Still, it’s a classic example of a small investment of time leading to a big improvement in performance and user experience.

If you think your company’s website could benefit from being a progressive web app (and believe me, it definitely could), you have a couple of options:

  1. Arm yourself with a copy of Going Offline and give it a go yourself. Or
  2. Get in touch with Clearleft. We can help you. (See, I can say that with a straight face now that we’re practicing what we preach.)

Either way, don’t dilly dally …like I did.

HTTPS + service worker + web app manifest = progressive web app

I gave a quick talk at the Delta V conference in London last week called Any Site can be a Progressive Web App. I had ten minutes, but frankly I only needed enough time to say the title of the talk because, well, that was also the message.

There’s a common misconception that making a Progressive Web App means creating a Single Page App with an app-shell architecture. But the truth is that literally any website can benefit from the performance boost that results from the combination of HTTPS + Service Worker + Web App Manifest.

See how I define a progressive web app as being HTTPS + service worker + web app manifest? I’ve been doing that for a while. Here’s a post from last year called Progressing the web:

Literally any website can be a progressive web app:

That last step can be tricky if you’re new to service workers, but it’s not unsurmountable. It’s certainly a lot easier than completely rearchitecting your existing website to be a JavaScript-driven single page app.

Later I wrote a post called What is a Progressive Web App? where I compared the definition to responsive web design.

Regardless of the specifics of the name, what I like about Progressive Web Apps is that they have a clear definition. It reminds me of Responsive Web Design. Whatever you think of that name, it comes with a clear list of requirements:

  1. A fluid layout,
  2. Fluid images, and
  3. Media queries.

Likewise, Progressive Web Apps consist of:

  1. HTTPS,
  2. A service worker, and
  3. A Web App Manifest.

There’s more you can do in addition to that (just as there’s plenty more you can do on a responsive site), but the core definition is nice and clear.

But here’s the thing. Outside of the confines of my own website, it’s hard to find that definition anywhere.

On Google’s developer site, their definition uses adjectives like “reliable”, “fast”, and “engaging”. Those are all great adjectives, but more useful to a salesperson than a developer.

Over on the Mozilla Developer Network, their section on progressive web apps states:

Progressive web apps use modern web APIs along with traditional progressive enhancement strategy to create cross-platform web applications. These apps work everywhere and provide several features that give them the same user experience advantages as native apps. 

Hmm …I’m not so sure about that comparison to native apps (and I’m a little disturbed that the URL structure is /Apps/Progressive). So let’s click through to the introduction:

PWAs are web apps developed using a number of specific technologies and standard patterns to allow them to take advantage of both web and native app features.

Okay. Specific technologies. That’s good to hear. But instead of then listing those specific technologies, we’re given another list of adjectives (discoverable, installable, linkable, etc.). Again, like Google’s chosen adjectives, they’re very nice and desirable, but not exactly useful to someone who wants to get started making a progressive web app. That’s why I like to cut to the chase and say:

  • You need to be running on HTTPS,
  • Then you can add a service worker,
  • And don’t forget to add a web app manifest file.

If you do that, you’ve got a progressive web app. Now, to be fair, there’a lot that I’m leaving out. Your site should be fast. Your site should be responsive (it is, after all, on the web). There’s not much point mucking about with service workers if you haven’t sorted out the basics first. But those three things—HTTPS + service worker + web app manifest—are specifically what distinguishes a progressive web app. You can—and should—have a reliable, fast, engaging website before turning it into a progressive web app.

Jason has been thinking about progressive web apps a lot lately (he should write a book or something), and he said to me:

I agree with you on the three things that comprise a PWA, but as far as I can tell, you’re the first to declare it as such.

I was quite surprised by that. I always assumed that I was repeating the three ingredients of a progressive web app, not defining them. But looking through all the docs out there, Jason might be right. It’s surprising because I assumed it was obvious why those three things comprise a progressive web app—it’s because they’re testable.

Lighthouse, PWA Builder, Sonarwhal and other tools that evaluate your site will measure its progressive web app score based on the three defining factors (HTTPS, service worker, web app manifest). Then there’s Android’s Add to Home Screen prompt. Here finally we get a concrete description of what your site needs to do to pass muster:

  • Includes a web app manifest…
  • Served over HTTPS (required for service workers)
  • Has registered a service worker with a fetch event handler

(Although, as of this month, Chrome will no longer show the prompt automatically—you also have to write some JavaScript to handle the beforeinstallprompt  event).

Anyway, if you’re looking to turn your website into a progressive web app, here’s what you need to do (assuming it’s already performant and responsive):

  1. Switch over to HTTPS. Certbot can help you here.
  2. Add a web app manifest.
  3. Add a service worker to your site so that it responds even when there’s no network connection.

That last step might sound like an intimidating prospect, but help is at hand: I wrote Going Offline for exactly this situation.

Designing Progressive Web Apps by Jason Grigsby

It’s the afternoon of the second day of An Event Apart Seattle and Jason is talking about Designing Progressive Web Apps. These are my notes…

Jason wants to talk about a situation you might find yourself in. You’re in a room and in walks the boss, who says “We need a progressive web app.” Now everyone is asking themselves “What is a progressive web app?” Or maybe “How does the CEO even know about progressive web apps?”

Well, trade publications are covering progressive web apps. Lots of stats and case studies are being published. When executives see this kind of information, they don’t want to get left out. Jason keeps track of this stuff at PWA Stats.

Answering the question “What is a progressive web app?” is harder than it should be. The phrase was coined by Frances Berriman and Alex Russell. They listed ten characteristics that defined progressive web apps. The “linkable” and “progressive” characteristics are the really interesting and new characteristics. We’ve had technologies before (like Adobe Air) that tried to make app-like experiences, but they weren’t really of the web. Progressive web apps are different.

Despite this list of ten characteristics, even people who are shipping progressive web apps find it hard to define the damn thing. The definition on Google’s developer site keeps changing. They reduced the characteristics from ten to six. Then it became “reliable, fast, and engaging.” What does that mean? Craigslist is reliable, fast, and engaging—does that mean it’s a progressive web app.

The technical definition is useful (kudos to me, says Jason):

  1. HTTPS
  2. service worker
  3. manifest file

If you don’t have those three things, it’s not a progressive web app.

We should definitely use HTTPS if we want make life harder for the NSA. Also browser makers are making APIs available only under HTTPS. By July, Chrome will mark HTTP sites as insecure. Every site should be under HTTPS.

Service workers are where the power is. They act as a proxy. They allow us to say what we want to cache, what we want to go out to the network for; things that native apps have been able to do for a while. With progressive web apps we can cache the app shell and go to the network for content. Service workers can provide a real performance boost.

A manifest file is simply a JSON file. It’s short and clear. It lists information about the app: icons, colours, etc.

Once you provide those three things, you get benefits. Chrome and Opera on Android will prompt to add the app to the home screen.

So that’s what’s required for progressive web apps, but there’s more to them than that (in the same way there’s more to responsive web design than the three requirements in the baseline definition).

The hype around progressive web apps can be a bit of a turn-off. It certainly was for Jason. When he investigated the technologies, he wondered “What’s the big deal?” But then he was on a panel at a marketing conference, and everyone was talking about progressive web apps. People’s expectations of what you could do on the web really hadn’t caught up with what we can do now, and the phrase “progressive web app” gives us a way to encapsulate that. As Frances says, the name isn’t for us; it’s for our boss or marketer.

Jason references my post about using the right language for the right audience.

Should you have a progressive web app? Well, if you have a website, then the answer is almost certainly “Yes!” If you make money from that website, the answer is definitely “Yes!”

But there’s a lot of FUD around progressive web apps. It brings up the tired native vs. web battle. Remember though that not 100% of your users or customers have your app installed. And it’s getting harder to convince people to install apps. The average number of apps installed per month is zero. But your website is often a customer’s first interaction with your company. A better web experience can only benefit you.

Often, people say “The web can’t do…” but a lot of the time that information is out of date. There are articles out there with outdated information. One article said that progressive web apps couldn’t access the camera, location, or the fingerprint sensor. Yet look at Instagram’s progressive web app: it accesses the camera. And just about every website wants access to your location these days. And Jason knows you can use your fingerprint to buy things on the web because he accidentally bought socks when he was trying to take a screenshot of the J.Crew website on his iPhone. So the author of that article was just plain wrong. The web can do much more than we think it can.

Another common objection is “iOS doesn’t support progressive web apps”. Well, as of last week that is no longer true. But even when that was still true, people who had implemented progressive web apps were seeing increased conversion even on iOS. That’s probably because, if you’ve got the mindset for building a progressive web app, you’re thinking deeply about performance. In many ways, progressive web apps are a trojan horse for performance.

These are the things that people think about when it comes to progressive web apps:

  1. Making it feel like a app
  2. Installation and discovery
  3. Offline mode
  4. Push notifications
  5. Beyond progressive web app

Making it feel like a app

What is an app anyway? Nobody can define it. Once again, Jason references my posts on this topic (how “app” is like “obscenity” or “brunch”).

A lot of people think that “app-like” means making it look native. But that’s a trap. Which operating system will you choose to emulate? Also, those design systems change over time. You should define your own design. Make it an exceptional experience regardless of OS.

It makes more sense to talk in terms of goals…

Goal: a more immersive experience.

Possible solution: removing the browser chrome and going fullscreen?

You can define this in the manifest file. But as you remove the browser chrome, you start to lose things that people rely on: the back button, the address bar. Now you have to provide that functionality. If you move to a fullscreen application you need to implement sharing, printing, and the back button (and managing browser history is not simple). Remember that not every customer will add your progressive web app to their home screen. Some will have browser chrome; some won’t.

Goal: a fast fluid experience.

Possible solution: use an app shell model.

You want smooth pages that don’t jump around as the content loads in. The app shell makes things seem faster because something is available instantly—it’s perceived performance. Basically you’re building a single page application. That’s a major transition. But thankfully, you don’t have to do it! Progressive web apps don’t have to be single page apps.

Goal: an app with personality.

Possible solution: Animated transitions and other bits of UI polish.

Really, it’s all about delight.

Installation and discovery

In your manifest file you can declare a background colour for the startup screen. You can also declare a theme colour—it’s like you’re skinning the browser chrome.

You can examine the manifest files for a site in Chrome’s dev tools.

Once you’ve got a progressive web app, some mobile browsers will start prompting users to add it to their home screen. Firefox on Android displays a little explainer the first time you visit a progressive web app. Chrome and Opera have add-to-homescreen banners which are a bit more intrusive. The question of when they show up keeps changing. They use a heuristic to decide this. The heuristic has been changed a few times already. One thing you should consider is suppressing the banner until it’s an optimal time. Flipkart do this: they only allow it on the order confirmation page—the act of buying something makes it really likely that someone will add the progressive web app to their home screen.

What about app stores? We don’t need them for progressive web apps—they’re on the web. But Microsoft is going to start adding progressive web apps to their app store. They’ve built a site called PWA Builder to help you with your progressive web app.

On the Android side, there’s Trusted Web Activity which is kind of like PhoneGap—it allows you to get a progressive web app into the Android app store.

But remember, your progressive web app is your website so all the normal web marketing still applies.

Offline mode

A lot of organisations say they have no need for offline functionality. But everyone has a need for some offline capability. At the very least, you can provide a fallback page, like Trivago’s offline maze game.

You can cache content that has been recently viewed. This is what Jason does on the Cloud Four site. They didn’t want to make any assumptions about what people might want, so they only cache pages as people browse around the site.

If you display cached information, you might want to display how stale the information is e.g. for currency exchange rates.

Another option is to let people choose what they want to keep offline. The Financial Times does this. They also pre-cache the daily edition.

If you have an interactive application, you could queue tasks and then carry them out when there’s a connection.

Or, like Slack does, don’t let people write something if they’re offline. That’s better than letting someone write something and then losing it.

Workbox is a handy library for providing offline functionality.

Push notifications

The JavaScript for push notifications is relatively easy, says Jason. It’s the back-end stuff that’s hard. That’s because successful push notifications are personalised. But to do that means doing a lot more work on the back end. How do you integrate with preferences? Which events trigger notifications?

There are third-party push notification services that take care of a lot of this for you. Jason has used OneSignal.

Remember that people are really annoyed by push notifications. Don’t ask for permission immediately. Don’t ask someone to marry you on a first date. On Cloud Four’s blog, they only prompt after the user has read an article.

Twitter’s progressive web app does this really well. It’s so important that you do this well: if a user says “no” to your push notification permission request, you will never be able to ask them again. There used to be three options on Chrome: allow, block, or close. Now there are just two: allow or block.

Beyond progressive web apps

There are a lot of APIs that aren’t technically part of progressive web apps but get bundled in with them. Like the Credentials Management API or the Payment Request API (which is converging with ApplePay).

So how should you plan your progressive web app launch? Remember it’s progressive. You can keep adding features. Each step along the way, you’re providing value to people.

Start with some planning and definition. Get everyone in a room and get a common definition of what the ideal progressive web app would look like. Remember there’s a continuum of features for all five of the things that Jason has outlined here.

Benchmark your existing site. It will help you later on.

Assess your current website. Is the site reasonably fast? Is it responsive? Fix those usability issues first.

Next, do the baseline. Switch to HTTPS. Add a manifest file. Add a service worker. Apart from the HTTPS switch, this can all be done on the front end. Don’t wait for all three: ship each one when they’re ready.

Then do front-end additions: pre-caching pages, for example.

Finally, there are the larger initiatives (with more complex APIs). This is where your initial benchmarking really pays off. You can demonstrate the value of what you’re proposing.

Every step on the path to a progressive web app makes sense on its own. Figure out where you want to go and start that journey.

See also:

Offline itineraries with service workers

The Trivago website is a progressive web app. That means it

  1. is served over HTTPS,
  2. has a web app manifest JSON file, and it
  3. has a service worker script.

The service worker provides an opportunity for a nice bit of fun branding—if you lose your internet connection, the site provides a neat little maze game you can play. Cute!

That’s a fairly simple example of how service workers can enhance the user experience when the dreaded offline situation arises. But it strikes me that the travel industry is the perfect place to imagine other opportunities for offline enhancements.

Travel sites often provide itineraries—think airlines, trains, or hotels. The itineraries consist of places, times, and contact information. This is exactly the kind of information that you might find yourself trying to retrieve in an emergency situation, like maybe in a cab on the way to the airport or train station. Perhaps you’re stuck in traffic, in a tunnel. Or maybe you don’t have a data plan for the country you’re currently in. Either way, wouldn’t it be great if you could hit the website for your airline or hotel and get your itinerary, even if you’re offline.

Alright, let’s think this through…

Let’s assume that an individual itinerary has its own URL. That URL is a web page of information, mostly text, with perhaps an image or two (like a map). Now when you make your booking, let’s have the service worker cache that URL (and its assets) for offline access.

Hmm …but there’s a good chance that the device you make the booking on is not the same device that you’d have with you out and and about. Because caches are local to the browser, that’s a problem.

Okay, but of these kinds of sites have some kind of log-in mechanism. So we could update the log-in flow a bit: when a user logs in, check to see if they have any itineraries assigned to them, and if they do, fire off an event to the service worker (using postMessage) to cache the URLs of the itineraries.

Now that the itineraries are cached, the final step is to create a custom offline page. As well as the usual “Sorry, the internet’s down” message, we can say “Sorry, the internet’s down …but here are your itineraries”. (This is kind of like the pattern you see on blogs like mine, Ethan’s, or Mike’s—a custom offline page that lists cached URLs of articles you’ve previously visited).

That’s just one pattern off the top of my head. It’s fun to imagine the different ways that service workers could be used to enhance the experience of just about any site, but they seem particularly relevant to travel sites—dodgy internet connections and travelling go hand-in-hand. At Clearleft, we’ve been working with quite a few travel-related clients lately so that’s why these scenarios are on my mind: booking holidays, flights, and so on. But, as I’ve said before and I’ll say again, every website can benefit from becoming a progressive web app.

What is a Progressive Web App?

It seems like any new field goes through an inevitable growth spurt that involves “defining the damn thing.” For the first few years of the IA Summit, every second presentation seemed to be about defining what Information Architecture actually is. See also: UX. See also: Content Strategy.

Now it seems to be happening with Progressive Web Apps …which is odd, considering the damn thing is defined damn well.

I’ve written before about the naming of Progressive Web Apps. On the whole, I think it’s a pretty good term, especially if you’re trying to convince the marketing team.

Regardless of the specifics of the name, what I like about Progressive Web Apps is that they have a clear definition. It reminds me of Responsive Web Design. Whatever you think of that name, it comes with a clear list of requirements:

  1. A fluid layout,
  2. Fluid images, and
  3. Media queries.

Likewise, Progressive Web Apps consist of:

  1. HTTPS,
  2. A service worker, and
  3. A Web App Manifest.

There’s more you can do in addition to that (just as there’s plenty more you can do on a responsive site), but the core definition is nice and clear.

Except, for some reason, that clarity is being lost.

Here’s a post by Ben Halpern called What the heck is a “Progressive Web App”? Seriously.

I have a really hard time describing what a progressive web app actually is.

He points to Google’s intro to Progressive Web Apps:

Progressive Web Apps are user experiences that have the reach of the web, and are:

  • Reliable - Load instantly and never show the downasaur, even in uncertain network conditions.
  • Fast - Respond quickly to user interactions with silky smooth animations and no janky scrolling.
  • Engaging - Feel like a natural app on the device, with an immersive user experience.

Those are great descriptions of the benefits of Progressive Web Apps. Perfect material for convincing your clients or your boss. But that appears on developers.google.com …surely it would be more beneficial for that audience to know the technologies that comprise Progressive Web Apps?

Ben Halpern again:

Google’s continued use of the term “quality” in describing things leaves me with a ton of confusion. It really seems like they want PWA to be a general term that doesn’t imply any particular implementation, and have it be focused around the user experience, but all I see over the web is confusion as to what they mean by these things. My website is already “engaging” and “immersive”, does that mean it’s a PWA?

I think it’s important to use the right language for the right audience.

If you’re talking to the business people, tell them about the return on investment you get from Progressive Web Apps.

If you’re talking to the marketing people, tell them about the experiential benefits of Progressive Web Apps.

But if you’re talking to developers, tell them that a Progressive Web App is a website served over HTTPS with a service worker and manifest file.