Tags: pwas



Thursday, March 23rd, 2017

Retrofit Your Website as a Progressive Web App — SitePoint

Turning your existing website into a progressive web “app”—a far more appealing prospect than trying to create an entirely new app-shell architecture:

…they are an enhancement of your existing website which should take no longer than a few hours and have no negative effect on unsupported browsers.

Wednesday, March 15th, 2017

Progressive Web App questions

I got a nice email recently from Colin van Eenige. He wrote:

For my graduation project I’m researching the development of Progressive Web Apps and found your offline book called resilient web design. I was very impressed by the implementation of the website and it really was a nice experience.

I’m very interested in your vision on progressive web apps and what capabilities are waiting for us regarding offline content. Would it be fine if I’d send you some questions?

I said that would be fine, although I couldn’t promise a swift response. He sent me four questions. I finally got ‘round to sending my answers…

1. https://resilientwebdesign.com/ is an offline web book (progressive web app). What was the primary reason make it available like this (besides the other formats)?

Well, given the subject matter, it felt right that the canonical version of the book should be not just online, but made with the building blocks of the web. The other formats are all nice to have, but the HTML version feels (to me) like the “real” book.

Interestingly, it wasn’t too much trouble for people to generate other formats from the HTML (ePub, MOBI, PDF), whereas I think trying to go in the other direction would be trickier.

As for the offline part, that felt like a natural fit. I had already done that with a previous book of mine, HTML5 For Web Designers, which I put online a year or two after its print publication. In that case, I used AppCache for the offline functionality. AppCache is horrible, but this use case might be one of the few where it works well: a static book that’s never going to change. Cache invalidation is one of the worst parts of using AppCache so by not having any kinds of updates at all, I dodged that bullet.

But when it came time for Resilient Web Design, a service worker was definitely the right technology. Still, I’ve got AppCache in there as well for the browsers that don’t yet support service workers.

2. What effect you you think Progressive Web Apps will have on content consuming and do you think these will take over the purpose of some Native Apps?

The biggest effect that service workers could have is to change the expectations that people have about using the web, especially on mobile devices. Right now, people associate the web on mobile with long waits and horrible spammy overlays. Service workers can help solve that first part.

If people then start adding sites to their home screen, that will be a great sign that the web is really holding its own. But I don’t think we should get too optimistic about that: for a user, there’s no difference between a prompt on their screen saying “add to home screen” and a prompt on their screen saying “download our app”—they’re equally likely to be dismissed because we’ve trained people to dismiss anything that covers up the content they actually came for.

It’s entirely possible that websites could start taking over much of the functionality that previously was only possible in a native app. But I think that inertia and habit will keep people using native apps for quite some time.

The big exception is in markets where storage space on devices is in short supply. That’s where the decision to install a native app isn’t taken likely (given the choice between your family photos and an app, most people will reject the app). The web can truly shine here if we build lightweight, performant services.

Even in that situation, I’m still not sure how many people will end up adding those sites to their home screen (it might feel so similar to installing a native app that there may be some residual worry about storage space) but I don’t think that’s too much of a problem: if people get to a site via search or typing, that’s fine.

I worry that the messaging around “progressive web apps” is perhaps over-fetishising the home screen. I don’t think that’s the real battleground. The real battleground is in people’s heads; how they perceive the web and how they perceive native.

After all, if the average number of native apps installed in a month is zero, then that’s not exactly a hard target to match. :-)

3. What is your vision regarding Progressive Web Apps?

For me, progressive web apps don’t feel like a separate thing from making websites. I worry that the marketing of them might inflate expectations or confuse people. I like the idea that they’re simply websites that have taken their vitamins.

So my vision for progressive web apps is the same as my vision for the web: something that people use every day for all sorts of tasks.

I find it really discouraging that progressive web apps are becoming conflated with single page apps and the app shell model. Those architectural decisions have nothing to do with service workers, HTTPS, and manifest files. Yet I keep seeing the concepts used interchangeably. It would be a real shame if people chose not to use these great technologies just because they don’t classify what they’re building as an “app.”

If anything, it’s good ol’ fashioned content sites (newspapers, wikipedia, blogs, and yes, books) that can really benefit from the turbo boost of service worker+HTTPS+manifest.

I was at a conference recently where someone was given a talk encouraging people to build progressive web apps but discouraging people from doing it for their own personal sites. That’s a horrible, elitist attitude. I worry that this attitude is being codified in the term “progressive web app”.

4. What is the biggest learning you’ve had since working on Progressive Web Apps?

Well, like I said, I think that some people are focusing a bit too much on the home screen and not enough on the benefits that service workers can provide to just about any website.

My biggest learning is that these technologies aren’t for a specific subset of services, but can benefit just about anything that’s on the web. I mean, just using a service worker to explicitly cache static assets like CSS, JS, and some images is a no-brainer for almost any project.

So there you go—I’m very excited about the capabilities of these technologies, but very worried about how they’re being “sold”. I’m particularly nervous that in the rush to emulate native apps, we end up losing the very thing that makes the web so powerful: URLs.

Friday, February 17th, 2017


A useful tool to help you generate a manifest file, icons, and a service worker for your progressive web appsite.

Sunday, January 29th, 2017

We built a PWA from scratch - This is what we learned

A nice straightforward account of building and testing a progressive web a… I mean, website.

I think every website from now on should use some of the Progressive Web App features. It’s even confusing to call it “Apps” as it applies to all websites and apps.

Friday, January 27th, 2017

A practical guide to Progressive Web Apps for organisations who don’t know anything about Progressive Web Apps : Records Sound the Same

Sally gives a really good introduction to using service workers as a progressive enhancement.

Thursday, December 8th, 2016

Hey, Hey, Cloud Four is a PWA! - Cloud Four

Jason talks through the service worker strategy for his company website.

Sunday, December 4th, 2016

Installing web apps on phones (for real)

Henrik points to some crucial information that slipped under the radar at the Chrome Dev Summit—the Android OS is going to treat progressive web apps much more like regular native apps. This is kind of a big deal.

It’s a good time to go all in on the web. I can’t wait to see what the next few years bring. Personally, I feel like the web is well poised to replace the majority of apps we now get from app stores.

Thursday, November 17th, 2016

Less JavaScript

Every front-end developer at Clearleft went to FFConf last Friday: me, Mark, Graham, Charlotte, and Danielle. We weren’t about to pass up the opportunity to attend a world-class dev conference right here in our home base of Brighton.

The day was unsurprisingly excellent. All the speakers brought their A-game on a wide range of topics. Of course JavaScript was covered, but there was also plenty of mindfood on CSS, accessibility, progressive enhancement, dev tools, creative coding, and even emoji.

Normally FFConf would be a good opportunity to catch up with some Pauls from the Google devrel team, but because of an unfortunate scheduling clash this year, all the Pauls were at Chrome Dev Summit 2016 on the other side of the Atlantic.

I’ve been catching up on the videos from the event. There’s plenty of tech-related stuff: dev tools, web components, and plenty of talk about progressive web apps. But there was also a very, very heavy focus on performance. I don’t just mean performance at the shallow scale of file size and optimisation, but a genuine questioning of the impact of our developer workflows and tools.

In his talk on service workers (what else?), Jake makes the point that not everything needs to be a single page app, echoing Ada’s talk at FFConf.

He makes the point that if you really want fast rendering, nothing on the client side quite beats a server render.

They’ve written a lot of JavaScript to make this quite slow.

Unfortunately, all too often, I hear people say that a progressive web app must be a single page app. And I am not so sure. You might not need a single page app. A single page app can end up being a lot of work and slower. There’s a lot of cargo-culting around single page apps.

Alex followed up his barnstorming talk from the Polymer Summit with some more uncomfortable truths about how mobile phones work.

Cell networks are basically kryptonite to the protocols and assumptions that the web was built on.

And JavaScript frameworks aren’t helping. Quite the opposite.

But make no mistake: if you’re using one of today’s more popular JavaScript frameworks in the most naive way, you are failing by default. There is no sugarcoating this.

Today’s frameworks are mostly a sign of ignorance, or privilege, or both. The good news is that we can fix the ignorance.

Friday, October 28th, 2016

Working with mobile technology - Digital Service Manual - GOV.UK

Excellent guidelines from GDS on providing services that work well on mobile. The watchwords are:

  • responsive design,
  • progressive enhancement,
  • open data, and
  • emerging technology (service workers, notifications, etc.).

Native and hybrid apps are rarely justified.

Tuesday, October 18th, 2016


Laurie Voss has written a thoughtful article called Web development has two flavors of graceful degradation in response to Nolan Lawson’s recent article. But I’m afraid I don’t agree with Laurie’s central premise:

…web app development and web site development are so different now that they probably shouldn’t be called the same thing anymore.

This is an idea I keep returning to, and each time I do, I find that it just isn’t that simple. There are very few web thangs that are purely interactive without any content, and there are also very few web thangs that are purely passive without any interaction. Instead, it’s a spectrum. Quite often, the position on that spectrum changes according to the needs of the user at any particular time—are Twitter and Flicker web sites while I’m viewing text and images, but then transmogrify into web apps the moment I want add, update, or delete a piece of text or an image?

In any case, the more interesting question than “is something a web site or a web app?” is the question “why?” Why does it matter? In my experience, the answer to that question generally comes down to the kind of architectural approach that a developer will take.

That’s exactly what Laurie dives into in his post. For web apps, use one architectural approach—for web sites, use a different architectural approach. To summarise:

  • in a web app, front-load everything and rely on client-side JavaScript for all subsequent interaction,
  • in a web site, optimise for many page loads, and make sure you don’t rely on client-side JavaScript.

I’m oversimplifying here, but the general idea is:

  • build web apps with the single page app architecture,
  • build web sites with progressive enhancement.

That’s sensible advice, but I’m worried that it could lead to a tautological definition of what constitutes a web app:

  1. This is a web app so it’s built as a single page app.
  2. Why do you define it as a web app?
  3. Because it’s built as a single page app.

The underlying question of what makes something a web app is bypassed by the architectural considerations …but the architectural considerations should be based on that underlying question. Laurie says:

If you are developing an app, the user ideally loads the app exactly once — whether it’s over a slow connection or not.

And similarly:

But if you are developing a web site consisting of many discrete pages, the act of loading goes from a single event to the most common event.

I completely agree that the architectural approach of single page apps is better suited to some kinds of web thangs more than others. It’s a poor architectural choice for a content-based site like nasa.gov, for example. Progressive enhancement would make more sense there.

But I don’t think that the architectural choices need to be in opposition. It’s entirely possible to reconcile the two. It’s not always easy—and the further along that spectrum you are, the tougher it gets—but it’s doable. You can begin with progressive enhancement, and then build up to a single page app architecture for more capable browsers.

I think that’s going to get easier as frameworks adopt a more mixed approach. Almost all the major libraries are working on server-side rendering as a default. Ember is leading the way with FastBoot, and Angular Universal is following. Neither of them are doing it for reasons of progressive enhancement—they’re doing it for performance and SEO—but the upshot is that you can more easily build a web app that simultaneously uses progressive enhancement and a single-page app model.

I guess my point is that I don’t think we should get too locked into the idea of web apps and web sites requiring fundamentally different approaches, especially with the changes in the technologies we used to build them.

We’ve made the mistake in the past of framing problems as “either/or”, when in fact, the correct solution was “both!”:

  • you can either have a desktop site or a mobile site,
  • you can either have rich interactivity or accessibility,
  • you can either have a single page app or progressive enhancement.

We don’t have to choose. It might take more work, but we can have our web cake and eat it.

The false dichotomy that I’m most concerned about is the pernicious idea that offline functionality is somehow in opposition to progressive enhancement. Given the design of service workers, I find this proposition baffling.

This remark by Tom is the very definition of a false dichotomy:

People who say your site should work without JavaScript are actually hurting the people they think they’re helping.

He was also linking to Nolan’s article, which could indeed be read as saying that you should for offline instead of building with progressive enhancement. But I don’t think that’s what Nolan is saying (at least, I sincerely hope not). I think that Nolan is saying that we should prioritise the offline scenario over scenarios where JavaScript fails or isn’t available. That’s a completely reasonable thing to say. But the idea that we should build for the offline scenario instead of scenarios where JavaScript fails is absurdly reductionist. We don’t have to choose!

But I can certainly understand how developers might come to be believe that building a progressive web app is at odds with progressive enhancement. Having made a bunch of progressive web apps—Huffduffer, The Session, this site, I can testify that service workers work superbly as a layer on top of an existing site, but all the messaging around progressive web apps seems to fixated on the idea of the app-shell model (a small tweak to the single page app model, where a little bit of interface is available on the initial page load instead of requiring JavaScript for absolutely everything). Again, it’s entirely possible to reconcile the app-shell approach with server rendering and progressive enhancement, but nobody seems to be talking about that. Instead, all of the examples and demos are built with an assumption about JavaScript availability.

Assumptions are the problem. Whether it’s assumptions about screen size, assumptions about being able-bodied, assumptions about network connectivity, or assumptions about browser capabilities, I don’t think any assumptions are a safe bet. Now you might quite reasonably say that we have to make some assumptions when we’re building on the web, and you’d be right. But I think we should still aim to keep them to a minimum.

Tom’s tweet included a screenshot of this part of Nolan’s article:

As Benedict Evans has noted, the next billion people who are poised to come online will be using the internet almost exclusively through smartphones. And if Google’s plans with Android One are any indication, then we have a fairly good idea of what kind of devices the “next billion” will be using:

  • They’ll mostly be running Android.
  • They’ll have decent specs (1GB RAM, quad-core processors).
  • They’ll have an evergreen browser and WebView (Android 5+).
  • What they won’t have, however, is a reliable internet connection.

Those seem like a reasonable set of assumptions. But even there, things aren’t so simple. Will people really be using “an evergreen browser and WebView”? Millions of people use proxy browsers like Opera Mini, which means you can’t guarantee JavaScript availability beyond the initial page load. UC Browser—which can also run in proxy mode—is now the second most popular mobile browser in the world.

That’s just one nit-picky example, but what I’m getting at here is that it really isn’t safe to make any assumptions. When we must make assumptions, let’s try to make them a last resort.

And just to be clear here, I’m not saying that just because we can’t make assumptions about devices or browsers doesn’t mean that we can’t build rich interactive web apps that work offline. I’m saying that we can build rich interactive web apps that work offline and also work when JavaScript fails or isn’t supported.

You don’t have to choose between progressive enhancement and a single page app/progressive web app/app shell/other things with the word “app”.

Progressive enhancement is an architectural approach to building on the web. You don’t have to use it, but please try to remember that it is your choice to make. You can choose to build a web app using progressive enhancement or not—there is nothing inherent in the nature of the thing you’re building that precludes progressive enhancement.

Personally, I find progressive enhancement a sensible way to counteract any assumptions I might inadvertently make. Progressive enhancement increases the chances that the web site (or web app) I’m building is resilient to the kind of scenarios that I never would’ve predicted or anticipated.

That’s why I choose to use progressive enhancement …and build progressive web apps.

Wednesday, September 21st, 2016

Progressive Web Apps Simply Make Sense - Cloud Four

Progressive Web Apps versus native is the wrong question because every step on the path to a Progressive Web App makes sense on its own, irrespective of what a company does with their native apps.

Not all of your customers are going to have your app installed. For those who visit via the web, providing them with a better experience will make them happier and generate more revenue for your business.

It’s really that simple.

SpeedCurve | PWA Performance

Steve describes a script you can use on WebPageTest to simulate going offline so you can test how your progressive web app performs.

Monday, September 19th, 2016

An intro to progressive web apps | 8th Light

A nice introduction to progressive web apps. There’s a little bit of confusion about permissions—whether a site has been added to the home screen or not has no effect on the permissions granted to it (for things like push notifications)—but the wrap-up nails the advantages of using the web:

No more waiting to download an app, no more prompts for updating an app. From a developer perspective, it means we will be able to iterate a lot quicker. We don’t need to wait for app store approvals anymore, and we can deploy at our own leisure.

Another advantage that a progressive web app has over a native mobile app is that it is linkable, hence it is easier to share and, probably even more importantly, can be indexed by search engines. This makes discoverability of the app a lot better.

What, Exactly, Makes Something A Progressive Web App? | Infrequently Noted

Alex runs through the features that a progressive web app must have, should have, and would be nice to have.

In general, installability criteria are tightening. Today’s Good-To-Haves may become part of tomorrow’s baseline. The opposite is unlikely because at least one major browser has made a strong commitment to tightening up the rules for installability.

Right now, this is in the nice-to-have category:

Mobile-friendly, not mobile-only.

Personally, I’d put that in the must-have category, and not just for progressive web apps.

Anyway, read on for some advice on testing and tooling when it comes to evaluating progressive web apps.

Monday, September 12th, 2016

How Google And Others Are Plotting The Revenge Of The Web App | Fast Company | Business + Innovation

It’s always, um …”interesting” when a mainstream publication covers a topic from the web’s bikeshed. In this case, it’s progressive web apps, and—apart from the sensationalist headline—it’s actually not that bad at all.

Monday, September 5th, 2016

The Building Blocks Of Progressive Web Apps – Smashing Magazine

This is a really good overview of progressive web apps:

An ideal web app is a web page that has the best aspects of both the web and native apps. It should be fast and quick to interact with, fit the device’s viewport, remain usable offline and be able to have an icon on the home screen.

At the same time, it must not sacrifice the things that make the web great, such as the ability to link deep into the app and to use URLs to enable sharing of content. Like the web, it should work well across platforms and not focus solely on mobile. It should behave just as well on a desktop computer as in other form factors, lest we risk having another era of unresponsive m.example.com websites.

The imitation game

Jason shared some thoughts on designing progressive web apps. One of the things he’s pondering is how much you should try make your web-based offering look and feel like a native app.

This was prompted by an article by Owen Campbell-Moore over on Ev’s blog called Designing Great UIs for Progressive Web Apps. He begins with this advice:

Start by forgetting everything you know about conventional web design, and instead imagine you’re actually designing a native app.

This makes me squirm. I mean, I’m all for borrowing good ideas from other media—native apps, TV, print—but I don’t think that inspiration should mean imitation. For me, that always results in an interface that sits in a kind of uncanny valley of being almost—but not quite—like the thing it’s imitating.

With that out of the way, most of the recommendations in Owen’s article are sensible ideas about animation, input, and feedback. But then there’s recommendation number eight: Provide an easy way to share content:

PWAs are often shown in a context where the current URL isn’t easily accessible, so it is important to ensure the user can easily share what they’re currently looking at. Implement a share button that allows users to copy the URL to the clipboard, or share it with popular social networks.

See, when a developer has to implement a feature that the browser should be providing, that seems like a bad code smell to me. This is a problem that Opera is solving (and Google says it is solving, while meanwhile penalising developers who expose the URL to end users).

Anyway, I think my squeamishness about all the advice to imitate native apps is because it feels like a cargo cult. There seems to be an inherent assumption that native is intrinsically “better” than the web, and that the only way that the web can “win” is to match native apps note for note. But that misses out on all the things that only the web can do—instant distribution, low-friction sharing, and the ability to link to any other resource on the web (and be linked to in turn). Turning our beautifully-networked nodes into standalone silos just because that’s the way that native apps have to work feels like the cure that kills the patient.

If anything, my advice for building a progressive web app would be the exact opposite of Owen’s: don’t forget everything you’ve learned about web design. In my opinion, the term “progressive web app” can be read in order of priority:

  1. Progressive—build in a layered way so that anyone can access your content, regardless of what device or browser they’re using, rewarding the more capable browsers with more features.
  2. Web—you’re building for the web. Don’t lose sight of that. URLs matter. Accessibility matters. Performance matters.
  3. App—sure, borrow what works from native apps if it makes sense for your situation.

Jason asks questions about how your progressive web app will behave when it’s added to the home screen. How much do you match the platform? How do you manage going chromeless? And the big one: what do users expect?

Will people expect an experience that maps to native conventions? Or will they be more accepting of deviation because they came to the app via the web and have already seen it before installing it?

These are good questions and I share Jason’s hunch:

My gut says that we can build great experiences without having to make it feel exactly like an iOS or Android app because people will have already experienced the Progressive Web App multiple times in the browser before they are asked to install it.

In all the messaging from Google about progressive web apps, there’s a real feeling that the ability to install to—and launch from—the home screen is a real game changer. I’m not so sure that we should be betting the farm on that feature (the offline possibilities opened up by service workers feel like more of a game-changer to me).

People have been gleefully passing around the statistic that the average number of native apps installed per month is zero. So how exactly will we measure the success of progressive web apps against native apps …when the average number of progressive web apps installed per month is zero?

I like Android’s add-to-home-screen algorithm (although it needs tweaking). It’s a really nice carrot to reward the best websites with. But let’s not carried away. I think that most people are not going to click that “add to home screen” prompt. Let’s face it, we’ve trained people to ignore prompts like that. When someone is trying to find some information or complete a task, a prompt that pops up saying “sign up to our newsletter” or “download our native app” or “add to home screen” is a distraction to be dismissed. The fact that only the third example is initiated by the operating system, rather than the website, is irrelevant to the person using the website.

Getting the “add to home screen” prompt for https://huffduffer.com/ on Android Chrome.

My hunch is that the majority of people will still interact with your progressive web app via a regular web browser view. If, then, only a minority of people are going to experience your site launched from the home screen in a native-like way, I don’t think it makes sense to prioritise that use case.

The great thing about progressive web apps is that they are first and foremost websites. Literally everyone who interacts with your progressive web app is first going to do so the old-fashioned way, by following a link or typing in a URL. They may later add it to their home screen, but that’s just a bonus. I think it’s important to build progressive web apps accordingly—don’t pretend that it’s just like building a native app just because some people will be visiting via the home screen.

I’m worried that developers are going to think that progressive web apps are something that need to built from scratch; that you have to start with a blank slate and build something new in a completely new way. Now, there are some good examples of these kind of one-off progressive web apps—The Guardian’s RioRun is nicely done. But I don’t think that the majority of progressive web apps should fall into that category. There’s nothing to stop you taking an existing website and transforming it step-by-step into a progressive web app:

  1. Switch over to HTTPS if you aren’t already.
  2. Use a service worker, even if it’s just to provide a custom offline page and cache some static assets.
  3. Make a manifest file to point to an icon and specify some colours.

See? Not exactly a paradigm shift in how you approach building for the web …but those deceptively straightforward steps will really turbo-boost your site.

I’m really excited about progressive web apps …but mostly for the “progressive” and “web” parts. Maybe I’ll start calling them progressive web sites. Or progressive web thangs.

Monday, August 29th, 2016

How we made the RioRun progressive web app | Info | The Guardian

The devs at The Guardian walk through the process of building a progressive web app for the Olympics. There were some gotchas with the life cycle of service workers, but the pay-off was worth it:

Once you get there though, it’s quite magical when you load the page on a phone, switch it to airplane mode, reload, and continue using the app as though nothing was wrong.

Monday, August 8th, 2016

Progressive Enhancement for JavaScript App Developers | De Voorhoede

Build JS apps responsibly - cover your basics, render strategically and enhance into true apps.

Tuesday, July 19th, 2016

The best of Google I/O 2016 | Andrew Betts

Andrew picks out his favourite bits from this year’s Google I/O, covering web payments, CSS containment, and—of course—Service Workers and progressive web apps, although he does note (and I concur):

I wish Google would focus as much attention on ‘normal’ sites that perform navigations as they do on so called ‘app-shell’ (which is just a new name for single-page apps, as far as I can tell), but then many people will be building SPAs and these recipes will make those apps fly. In news publishing we seem to flip flop between traditional page navigations and SPAs, but I’ve never found a SPA news site (or a native app) that I really like more than a normal website. Maybe a really good progressive web app will change that. But I’m not convinced.

Still, as he says:

All this really just underscores how flexible ServiceWorker is and that with it we can disagree on what the right solution is, but we can all get what we want anyway.