Tags: web



Going offline at Indie Web Camp Düsseldorf

I’ve just come back from a ten-day trip to Germany. The trip kicked off with Indie Web Camp Düsseldorf over the course of a weekend.

IndieWebCamp Düsseldorf 2017

Once again the wonderful people at Sipgate hosted us in their beautiful building, and once again myself and Aaron helped facilitate the two days.

IndieWebCamp Düsseldorf 2017

Saturday was the BarCamp-like discussion day. Plenty of interesting topics were covered. I led a session on service workers, and that’s also what I decided to work on for the second day—that’s when the talking is done and we get down to making.

IndieWebCamp Düsseldorf 2017 IndieWebCamp Düsseldorf 2017 IndieWebCamp Düsseldorf 2017 IndieWebCamp Düsseldorf 2017

I like what Ethan is doing on his offline page. He shows a list of pages that have been cached, but instead of just listing URLs, he shows a title and description for each page.

I’ve already got a separate cache for pages that gets added to as the user browses around my site. I needed to figure out a way to store the metadata for those pages so that I could then display it on the offline page. I came up with a workable solution, and interestingly, it involved no changes to the service worker script at all.

When you visit any blog post, I put metadata about the page into localStorage (after first checking that there’s an active service worker):

if (navigator.serviceWorker && navigator.serviceWorker.controller) {
  window.addEventListener('load', function() {
    var data = {
      "title": "A minority report on artificial intelligence",
      "description": "Revisiting Spielberg’s films after a decade and a half.",
      "published": "May 7th, 2017",
      "timestamp": "1494171049"

In my case, I’m outputting the metadata from the server, but you could just as easily grab some from the DOM like this:

var data = {
  "title": document.querySelector("title").innerText,
  "description": document.querySelector("meta[name='description']").getAttribute("contents")

Meanwhile in my service worker, when you visit that same page, it gets added to a cache called “pages”. Both localStorage and the cache API are using URLs as keys. I take advantage of that on my offline page.

The nice thing about writing JavaScript on my offline page is that I know the page will only be seen by modern browsers that support service workers, so I can use all sorts of fancy from ES6, or whatever we’re calling it now.

I start by looping through the keys of the “pages” cache (that’s right—the cache API isn’t just for service workers; you can access it from any script). Then I check to see if there is a corresponding localStorage key with the same string (a URL). If there is, I pull the metadata out of local storage and add it to an array called browsingHistory:

const browsingHistory = [];
.then( cache => {
  .then(keys => {
    keys.forEach( request => {
      let data = JSON.parse(localStorage.getItem(request.url));
        if (data) {
          data['url'] = request.url;

Then I sort the list of pages in reverse chronological order:

browsingHistory.sort( (a,b) => {
  return b.timestamp - a.timestamp;

Now I loop through each page in the browsing history list and construct a link to each URL, complete with title and description:

let markup = '';
browsingHistory.forEach( data => {
  markup += `
<h2><a href="${ data.url }">${ data.title }</a></h2>
<p>${ data.description }</p>
<p class="meta">${ data.published }</p>

Finally I dump the constructed markup into a waiting div in the page with an ID of “history”:

let container = document.getElementById('history');
container.insertAdjacentHTML('beforeend', markup);

All those steps need to be wrapped inside the then clause attached to caches.open("pages") because the cache API is asynchronous.

There you have it. Now if you’re browsing adactio.com and your network connection drops (or my server goes offline), you can choose from a list of pages you’ve previously visited.

The current situation isn’t ideal though. I’ve got a clean-up operation in my service worker to limit the number of items stored in my “pages” cache. The cache never gets bigger than 35 items. But there’s no corresponding clean-up of metadata stored in localStorage. So there could be a lot more bits of metadata in local storage than there are pages in the cache. It’s not harmful, but it’s a bit wasteful.

I can’t do a clean-up of localStorage from my service worker because service workers can’t access localStorage. There’s a very good reason for that: the localStorage API is synchronous, and everything that happens in a service worker needs to be asynchronous.

Service workers can access indexedDB: it’s asynchronous. I could use indexedDB instead of localStorage, but I’m not a masochist. My best bet would be to use the localForage library, which wraps indexedDB in the simple syntax of localStorage.

Maybe I’ll do that at the next Homebrew Website Club here in Brighton.

Writing on the web

Some people have been putting Paul’s crazy idea into practice.

  • Mike revived his site a while back and he’s been posting gold dust ever since. I enjoy his no-holds-barred perspective on his time in San Francisco.
  • Garrett’s writing goes all the way back to 2005. The cumulative result is two fascinating interweaving narratives—one about his health, another about his business.
  • Charlotte has been documenting her move from Brighton to Sydney. Much as I love her articles about front-end development, I’m liking the slice-of-life updates on life down under even more.
  • Amber has a great way with words. As well as regularly writing on her blog, she’s two-thirds of the way through writing 100 words every day for 100 days.
  • Ethan has been writing about responsive design—of course—but it’s his more personal posts that make me really grateful for his site.
  • Jeffrey and Eric never stopped writing on their own sites. Sure, there’s good stuff on their about web design and development, but it’s the writing about their non-web lives that’s so powerful.

There are more people I could mention …but, to be honest, not that many more. Seems like most people are happy to only publish on Ev’s blog or not at all.

I know not everybody wants to write on the web, and that’s fine. But it makes me sad when people choose not to publish their thoughts because they think no-one will be interested, or that it’s all been said before. I understand where those worries come from, but I believe—no, I know—that they are unfounded.

It’s a world wide web out there. There’s plenty of room for everyone. And I, for one, love reading the words of others.

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.

Teaching in Porto, day four

Day one covered HTML (amongst other things), day two covered CSS, and day three covered JavaScript. Each one of those days involved a certain amount of hands-on coding, with the students getting their hands dirty with angle brackets, curly braces, and semi-colons.

Day four was a deliberate step away from all that. No more laptops, just paper. Whereas the previous days had focused on collaboratively working on a single document, today I wanted everyone to work on a separate site.

The sites were generated randomly. I made five cards with types of sites on them: news, social network, shopping, travel, and learning. Another five cards had subjects: books, music, food, pets, and cars. And another five cards had audiences: students, parents, the elderly, commuters, and teachers. Everyone was dealt a random card from each deck, resulting in briefs like “a travel site about food for the elderly” or “a social network about music for commuters.”

For a bit of fun, the first brainstorming exercise (run as a 6-up) was to come with potential names for this service—4 minutes for 6 ideas. Then we went around the table, shared the ideas, got feedback, and settled on the names.

Now I asked everyone to come up with a one-sentence mission statement for their newly-named service. This was a good way of teasing out the most important verbs and nouns, which led nicely into the next task: answering the question “what is the core functionality?”

If that sounds familiar, it’s because it’s the first part of the three-step process I outlined in Resilient Web Design:

  1. Identify core functionality.
  2. Make that functionality available using the simplest possible technology.
  3. Enhance!

We did some URL design, figuring out what structures would make sense for straightforward GET requests, like:

  • /things
  • /things/ID

Then, once it was clear what the primary “thing” was (a car, a book, etc.), I asked them to write down all the pieces that might appear on such a page; one post-it note per item e.g. “title”, “description”, “img”, “rating”, etc.

The next step involved prioritisation. They took those post-it notes and put them on the wall, but they had to put them in a vertical line from top to bottom in decreasing order of importance. This can be a challenge, but it’s better to solve these problems now rather than later.

Okay. I know asked them to “mark up” those vertical lists of post-it notes: writing HTML tag names by each one. By doing this before doing any visual design, it meant they were thinking about the meaning of the content first.

After that, we did a good ol’ fashioned classic 6-up sketching exercise, followed by critique (including a “designated dissenter” for each round). At this point, I was encouraging them to go crazy with ideas—they already had the core functionality figured out (with plain ol’ client/server requests and responses) so they could all the bells and whistles they wanted on top of that.

We finished up with a discussion of some of those bells and whistles, and how they could be used to improve the user experience: Ajax, geolocation, service workers, notifications, background sync …the sky’s the limit.

It was a whirlwind tour for just one day but I think it helped emphasise the importance of thinking about the fundamentals before adding enhancements.

This marked the end of the structured masterclass lessons. Tomorrow I’m around to answer any miscellaneous questions (if I can) and chat to the students individually while they work on their term projects.

Teaching in Porto, day three

Day two ended with a bit of a cliffhanger as I had the students mark up a document, but not yet style it. In the morning of day three, the styling began.

Rather than just treat “styling” as one big monolithic task, I broke it down into typography, colour, negative space, and so on. We time-boxed each one of those parts of the visual design. So everyone got, say, fifteen minutes to write styles relating to font families and sizes, then another fifteen minutes to write styles for colours and background colours. Bit by bit, the styles were layered on.

When it came to layout, we closed the laptops and returned to paper. Everyone did a quick round of 6-up sketching so that there was plenty of fast iteration on layout ideas. That was followed by some critique and dot-voting of the sketches.

Rather than diving into the CSS for layout—which can get quite complex—I instead walked through the approach for layout; namely putting all your layout styles inside media queries. To explain media queries, I first explained media types and then introduced the query part.

I felt pretty confident that I could skip over the nitty-gritty of media queries and cross-device layout because the next masterclass that will be taught at the New Digital School will be a week of responsive design, taught by Vitaly. I just gave them a taster—Vitaly can dive deeper.

By lunch time, I felt that we had covered CSS pretty well. After lunch it was time for the really challenging part: JavaScript.

The reason why I think JavaScript is challenging is that it’s inherently more complex than HTML or CSS. Those are declarative languages with fairly basic concepts at heart (elements, attributes, selectors, etc.), whereas an imperative language like JavaScript means entering the territory of logic, loops, variables, arrays, objects, and so on. I really didn’t want to get stuck in the weeds with that stuff.

I focused on the combination of JavaScript and the Document Object Model as a way of manipulating the HTML and CSS that’s already inside a browser. A lot of that boils down to this pattern:

When (some event happens), then (take this action).

We brainstormed some examples of this e.g. “When the user submits a form, then show a modal dialogue with an acknowledgement.” I then encouraged them to write a script …but I don’t mean a script in the JavaScript sense; I mean a script in the screenwriting or theatre sense. Line by line, write out each step that you want to accomplish. Once you’ve done that, translate each line of your English (or Portuguese) script into JavaScript.

I did quick demo as a proof of concept (which, much to my surprise, actually worked first time), but I was at pains to point out that they didn’t need to remember the syntax or vocabulary of the script; it was much more important to have a clear understanding of the thinking behind it.

With the remaining time left in the day, we ran through the many browser APIs available to JavaScript, from the relatively simple—like querySelector and Ajax—right up to the latest device APIs. I think I got the message across that, using JavaScript, there’s practically no limit to what you can do on the web these days …but the trick is to use that power responsibly.

At this point, we’ve had three days and we’ve covered three layers of web technologies: HTML, CSS, and JavaScript. Tomorrow we’ll take a step back from the nitty-gritty of the code. It’s going to be all about how to plan and think about building for the web before a single line of code gets written.

Teaching in Porto, day two

The second day in this week-long masterclass was focused on CSS. But before we could get stuck into that, there were some diversions and tangents brought on by left-over questions from day one.

This was not a problem. Far from it! The questions were really good. Like, how does a web server know that someone has permission to carry out actions via a POST request? What a perfect opportunity to talk about state! Cue a little history lesson on the web’s beginning as a deliberately stateless medium, followed by the introduction of cookies …for good and ill.

We also had a digression about performance, file sizes, and loading times—something I’m always more than happy to discuss. But by mid-morning, we were back on track and ready to tackle CSS.

As with the first day, I wanted to take a “long zoom” look at design and the web. So instead of diving straight into stylesheets, we first looked at the history of visual design: cave paintings, hieroglyphs, illuminated manuscripts, the printing press, the Swiss school …all of them examples of media where the designer knows where the “edges” of the canvas lie. Not so with the web.

So to tackle visual design on the web, I suggested separating layout from all the other aspects of visual design: colour, typography, contrast, negative space, and so on.

At this point we were ready to start thinking in CSS. I started by pointing out that all CSS boils down to one pattern:

selector {
  property: value;

The trick, then, is to convert what you want into that pattern. So “I want the body of the page to be off-white with dark grey text” in English is translated into the CSS:

body {
  background-color: rgb(225,225,255);
  color: rgb(51,51,51);

…and so one for type, contrast, hierarchy, and more.

We started applying styles to the content we had collectively marked up with post-it notes on day one. Then the students split into groups of two to create an HTML document each. Tomorrow they’ll be styling that document.

There were two important links that come up over the course of day two:

  1. A Dao Of Web Design by John Allsopp, and
  2. The CSS Zen Garden.

If all goes according to plan, we’ll be tackling the third layer of the web technology stack tomorrow: JavaScript.

Teaching in Porto, day one

Today was the first day of the week long “masterclass” I’m leading here at The New Digital School in Porto.

When I was putting together my stab-in-the-dark attempt to provide an outline for the week, I labelled day one as “How the web works” and gave this synopsis:

The internet and the web; how browsers work; a history of visual design on the web; the evolution of HTML and CSS.

There ended up being less about the history of visual design and CSS (we’ll cover that tomorrow) and more about the infrastructure that the web sits upon. Before diving into the way the web works, I thought it would be good to talk about how the internet works, which led me back to the history of communication networks in general. So the day started from cave drawings and smoke signals, leading to trade networks, then the postal system, before getting to the telegraph, and then telephone networks, the ARPANET, and eventually the internet. By lunch time we had just arrived at the birth of the World Wide Web at CERN.

It wasn’t all talk though. To demonstrate a hub-and-spoke network architecture I had everyone write down someone else’s name on a post-it note, then stand in a circle around me, and pass me (the hub) those messages to relay to their intended receiver. Later we repeated this exercise but with a packet-switching model: everyone could pass a note to their left or to their right. The hub-and-spoke system took almost a minute to relay all six messages; the packet-switching version took less than 10 seconds.

Over the course of the day, three different laws came up that were relevant to the history of the internet and the web:

Metcalfe’s Law
The value of a network is proportional to the square of the number of users.
Postel’s Law
Be conservative in what you send, be liberal in what you accept.
Sturgeon’s Law
Ninety percent of everything is crap.

There were also references to the giants of hypertext: Ted Nelson, Vannevar Bush, and Douglas Engelbart—for a while, I had the mother of all demos playing silently in the background.

After a most-excellent lunch in a nearby local restaurant (where I can highly recommend the tripe), we started on the building blocks of the web: HTTP, URLs, and HTML. I pulled up the first ever web page so that we could examine its markup and dive into the wonder of the A element. That led us to the first version of HTML which gave us enough vocabulary to start marking up documents: p, h1-h6, ol, ul, li, and a few others. We went around the room looking at posters and other documents pinned to the wall, and starting marking them up by slapping on post-it notes with opening and closing tags on them.

At this point we had covered the anatomy of an HTML element (opening tags, closing tags, attribute names and attribute values) as well as some of the history of HTML’s expanding vocabulary, including elements added in HTML5 like section, article, and nav. But so far everything was to do with marking up static content in a document. Stepping back a bit, we returned to HTTP, and talked about difference between GET and POST requests. That led in to ways of sending data to a server, which led to form fields and the many types of inputs at our disposal: text, password, radio, checkbox, email, url, tel, datetime, color, range, and more.

With that, the day drew to a close. I feel pretty good about what we covered. There was a lot of groundwork, and plenty of history, but also plenty of practical information about how browsers interpret HTML.

With the structural building blocks of the web in place, tomorrow is going to focus more on the design side of things.

Audio book

I’ve recorded each chapter of Resilient Web Design as MP3 files that I’ve been releasing once a week. The final chapter is recorded and released so my audio work is done here.

If you want subscribe to the podcast, pop this RSS feed into your podcast software of choice. Or use one of these links:

Or if you can have it as one single MP3 file to listen to as an audio book. It’s two hours long.

So, for those keeping count, the book is now available as HTML, PDF, EPUB, MOBI, and MP3.

Making Resilient Web Design work offline

I’ve written before about taking an online book offline, documenting the process behind the web version of HTML5 For Web Designers. A book is quite a static thing so it’s safe to take a fairly aggressive offline-first approach. In fact, a static unchanging book is one of the few situations that AppCache works for. Of course a service worker is better, but until AppCache is removed from browsers (and until service worker is supported across the board), I’m using both. I wouldn’t recommend that for most sites though—for most sites, use a service worker to enhance it, and avoid AppCache like the plague.

For Resilient Web Design, I took a similar approach to HTML5 For Web Designers but I knew that there was a good chance that some of the content would be getting tweaked at least for a while. So while the approach is still cache-first, I decided to keep the cache fairly fresh.

Here’s my service worker. It starts with the usual stuff: when the service worker is installed, there’s a list of static assets to cache. In this case, that list is literally everything; all the HTML, CSS, JavaScript, and images for the whole site. Again, this is a pattern that works well for a book, but wouldn’t be right for other kinds of websites.

The real heavy lifting happens with the fetch event. This is where the logic sits for what the service worker should do everytime there’s a request for a resource. I’ve documented the logic with comments:

// Look in the cache first, fall back to the network
  // CACHE
  // Did we find the file in the cache?
      // If so, fetch a fresh copy from the network in the background
      // NETWORK
          // Stash the fresh copy in the cache
  // If the file wasn't in the cache, make a network request
      // Stash a fresh copy in the cache in the background
  // If the request is for an image, show an offline placeholder
  // If the request is for a page, show an offline message

So my order of preference is:

  1. Try the cache first,
  2. Try the network second,
  3. Fallback to a placeholder as a last resort.

Leaving aside that third part, regardless of whether the response is served straight from the cache or from the network, the cache gets a top-up. If the response is being served from the cache, there’s an additional network request made to get a fresh copy of the resource that was just served. This means that the user might be seeing a slightly stale version of a file, but they’ll get the fresher version next time round.

Again, I think this acceptable for a book where the tweaks and changes should be fairly minor, but I definitely wouldn’t want to do it on a more dynamic site where the freshness matters more.

Here’s what it usually likes like when a file is served up from the cache:

  .then( responseFromCache => {
  // Did we find the file in the cache?
  if (responseFromCache) {
      return responseFromCache;

I’ve introduced an extra step where the fresher version is fetched from the network. This is where the code can look a bit confusing: the network request is happening in the background after the cached file has already been returned, but the code appears before the return statement:

  .then( responseFromCache => {
  // Did we find the file in the cache?
  if (responseFromCache) {
      // If so, fetch a fresh copy from the network in the background
          // NETWORK
          .then( responseFromFetch => {
              // Stash the fresh copy in the cache
              .then( cache => {
                  cache.put(request, responseFromFetch);
      return responseFromCache;

It’s asynchronous, see? So even though all that network code appears before the return statement, it’s pretty much guaranteed to complete after the cache response has been returned. You can verify this by putting in some console.log statements:

.then( responseFromCache => {
  if (responseFromCache) {
          .then( responseFromFetch => {
              console.log('Got a response from the network.');
              .then( cache => {
                  cache.put(request, responseFromFetch);
      console.log('Got a response from the cache.');
      return responseFromCache;

Those log statements will appear in this order:

Got a response from the cache.
Got a response from the network.

That’s the opposite order in which they appear in the code. Everything inside the event.waitUntil part is asynchronous.

Here’s the catch: this kind of asynchronous waitUntil hasn’t landed in all the browsers yet. The code I’ve written will fail.

But never fear! Jake has written a polyfill. All I need to do is include that at the start of my serviceworker.js file and I’m good to go:

// Import Jake's polyfill for async waitUntil

I’m also using it when a file isn’t found in the cache, and is returned from the network instead. Here’s what the usual network code looks like:

  .then( responseFromFetch => {
    return responseFromFetch;

I want to also store that response in the cache, but I want to do it asynchronously—I don’t care how long it takes to put the file in the cache as long as the user gets the response straight away.

Technically, I’m not putting the response in the cache; I’m putting a copy of the response in the cache (it’s a stream, so I need to clone it if I want to do more than one thing with it).

  .then( responseFromFetch => {
    // Stash a fresh copy in the cache in the background
    let responseCopy = responseFromFetch.clone();
      .then( cache => {
          cache.put(request, responseCopy);
    return responseFromFetch;

That all seems to be working well in browsers that support service workers. For legacy browsers, like Mobile Safari, there’s the much blunter caveman logic of an AppCache manifest.

Here’s the JavaScript that decides whether a browser gets the service worker or the AppCache:

if ('serviceWorker' in navigator) {
  // If service workers are supported
} else if ('applicationCache' in window) {
  // Otherwise inject an iframe to use appcache
  var iframe = document.createElement('iframe');
  iframe.setAttribute('src', '/appcache.html');
  iframe.setAttribute('style', 'width: 0; height: 0; border: 0');

Either way, people are making full use of the offline nature of the book and that makes me very happy indeed.

The many formats of Resilient Web Design

If you don’t like reading in a web browser, you might like to know that Resilient Web Design is now available in more formats.

Jiminy Panoz created a lovely EPUB version. I tried it out in Apple’s iBooks app and it looks great. I tried to submit it to the iBooks store too, but that process threw up a few too many roadblocks.

Oliver Williams has created a MOBI version. That’s means you can read it on a Kindle. I plugged my old Kindle into my computer, dragged that file onto its disc image, and it worked a treat.

And there’s always the PDF versions; one in portrait and another in landscape format. Those were generated straight from the print styles.

Oh, and there’s the podcast. I’ve only released two chapters so far. The Christmas break and an untimely cold have slowed down the release schedule a little bit.

I’d love to make a physical, print-on-demand version of Resilient Web Design available—maybe through Lulu—but my InDesign skills are non-existent.

If you think the book should be available in any other formats, and you fancy having a crack at it, please feel free to use the source files.

Deep linking with fragmentions

When I was marking up Resilient Web Design I wanted to make sure that people could link to individual sections within a chapter. So I added IDs to all the headings. There’s no UI to expose that though—like the hover pattern that some sites use to show that something is linkable—so unless you know the IDs are there, there’s no way of getting at them other than “view source.”

But if you’re reading a passage in Resilient Web Design and you highlight some text, you’ll notice that the URL updates to include that text after a hash symbol. If that updated URL gets shared, then anyone following it should be sent straight to that string of text within the page. That’s fragmentions in action:

Fragmentions find the first matching word or phrase in a document and focus its closest surrounding element. The match is determined by the case-sensitive string following the # (or ## double-hash)

It’s a similar idea to Eric and Simon’s proposal to use CSS selectors as fragment identifiers, but using plain text instead. You can find out more about the genesis of fragmentions from Kevin. I’m using Jonathon Neal’s script with some handy updates from Matthew.

I’m using the fragmention support to power the index of the book. It relies on JavaScript to work though, so Matthew has come to the rescue again and created a version of the site with IDs for each item linked from the index (I must get around to merging that).

The fragmention functionality is ticking along nicely with one problem…

I’ve tweaked the typography of Resilient Web Design to within an inch of its life, including a crude but effective technique to avoid widowed words at the end of a paragraph. The last two words of every paragraph are separated by a UTF-8 no-break space character instead of a regular space.

That solves the widowed words problem, but it confuses the fragmention script. Any selected text that includes the last two words of a paragraph fails to match. I’ve tried tweaking the script, but I’m stumped. If you fancy having a go, please have at it.

Update: And fixed! Thanks to Lee.

Print styles

I really wanted to make sure that the print styles for Resilient Web Design were pretty good—or at least as good as they could be given the everlasting lack of support for many print properties in browsers.

Here’s the first thing I added:

@media print {
  @page {
    margin: 1in 0.5in 0.5in;
    orphans: 4;
    widows: 3;

That sets the margins of printed pages in inches (I could’ve used centimetres but the numbers were nice and round in inches). The orphans: 4 declaration says that if there’s less than 4 lines on a page, shunt the text onto the next page. And widows: 3 declares that there shouldn’t be less than 3 lines left alone on a page (instead more lines will be carried over from the previous page).

I always get widows and orphans confused so I remind myself that orphans are left alone at the start; widows are left alone at the end.

I try to make sure that some elements don’t get their content split up over page breaks:

@media print {
  p, li, pre, figure, blockquote {
    page-break-inside: avoid;

I don’t want headings appearing at the end of a page with no content after them:

@media print {
  h1,h2,h3,h4,h5 {
    page-break-after: avoid;

But sections should always start with a fresh page:

@media print {
  section {
    page-break-before: always;

There are a few other little tweaks to hide some content from printing, but that’s pretty much it. Using print preview in browsers showed some pretty decent formatting. In fact, I used the “Save as PDF” option to create the PDF versions of the book. The portrait version comes from Chrome’s preview. The landscape version comes from Firefox, which offers more options under “Layout”.

For some more print style suggestions, have a look at the article I totally forgot about print style sheets. There’s also tips and tricks for print style sheets on Smashing Magazine. That includes a clever little trick for generating QR codes that only appear when a document is printed. I’ve used that technique for some page types over on The Session.

The typography of a web book

I’m a sucker for classic old-style serif typefaces: Caslon, Baskerville, Bembo, Garamond …I love ‘em. That’s probably why I’ve always found the typesetting in Edward Tufte’s books so appealing—he always uses a combination of Bembo for body copy and Gill Sans for headings.

Earlier this year I stumbled on a screen version of Bembo used for Tufte’s digital releases called ET Book. Best of all, it’s open source:

ET Book is a Bembo-like font for the computer designed by Dmitry Krasny, Bonnie Scranton, and Edward Tufte. It is free and open-source.

When I was styling Resilient Web Design, I knew that the choice of typeface would be one of the most important decisions I would make. Remembering that open source ET Book font, I plugged it in to see how it looked. I liked what I saw. I found it particularly appealing when it’s full black on full white at a nice big size (with lower contrast or sizes, it starts to get a bit fuzzy).

I love, love, love the old-style numerals of ET Book. But I was disappointed to see that ligatures didn’t seem to be coming through (even when I had enabled them in CSS). I mentioned this to Rich and of course he couldn’t resist doing a bit of typographic sleuthing. It turns out that the ligature glyphs are there in the source files but the files needed a little tweaking to enable them. Because the files are open source, Rich was able to tweak away to his heart’s content. I then took the tweaked open type files and ran them through Font Squirrel to generate WOFF and WOFF2 files. I’ve put them on Github.

For this book, I decided that the measure would be the priority. I settled on a measure of around 55 to 60 characters—about 10 or 11 words per line. I used a max-width of 27em combined with Mike’s brilliant fluid type technique to maintain a consistent measure.

It looks great on small-screen devices and tablets. On large screens, the font size starts to get really, really big. Personally, I like that. Lots of other people like it too. But some people really don’t like it. I should probably add a font-resizing widget for those who find the font size too shocking on luxuriously large screens. In the meantime, their only recourse is to fork the CSS to make their own version of the book with more familiar font sizes.

The visceral reaction a few people have expressed to the font size reminds me of the flak Jeffrey received when he redesigned his personal site a few years back:

Many people who’ve visited this site since the redesign have commented on the big type. It’s hard to miss. After all, words are practically the only feature I haven’t removed. Some of the people say they love it. Others are undecided. Many are still processing. A few say they hate it and suggest I’ve lost my mind.

I wonder how the people who complained then are feeling now, a few years on, in a world with Medium in it? Jeffrey’s redesign doesn’t look so extreme any more.

Resilient Web Design will be on the web for a very, very, very long time. I’m curious to see if its type size will still look shockingly large in years to come.

Introducing Resilient Web Design

I wrote a thing. The thing is a book. But the book is not published on paper. This book is on the web. It’s a web book. Or “wook” if you prefer …please don’t prefer. Here it is:

Resilient Web Design.

It’s yours for free.

Much of the subject matter will be familiar if you’ve seen my conference talks from the past couple of years, particularly Enhance! and Resilience. But the book ended up taking some twists and turns that surprised me. It turned out to be a bit of a history book: the history of design, the history of the web.

Resilient Web Design is a short book. It’s between sixteen and seventeen megawords long. You could read the whole thing in a couple of hours. Or—because the book has seven chapters—you could take fifteen to twenty minutes out of a day to read one chapter and you’d have read the whole thing done in a week.

If you make websites in any capacity, I hope that this book will resonate with you. Even if you don’t make websites, I still hope there’s an interesting story in there for you.

You can read the whole book on the web, but if you’d rather have a single file to carry around, I’ve made some PDFs as well: one in portrait, one in landscape.

I’ve licensed the book quite liberally. It’s released under a Creative Commons attribution share-alike licence. That means you can re-use the material in any way you want (even commercial usage) as long as you provide some attribution and use the same licence. So if you’d like to release the book in some other format like ePub or anything, go for it.

I’m currently making an audio version of Resilient Web Design. I’ll be releasing it one chapter at a time as a podcast. Here’s the RSS feed if you want to subscribe to it. Or you can subscribe directly from iTunes.

I took my sweet time writing this book. I wrote the first chapter in March 2015. I wrote the last chapter in May 2016. Then I sat on it for a while, figuring out what to do with it. Eventually I decided to just put the whole thing up on the web—it seems fitting.

Whereas the writing took over a year of solid procrastination, making the website went surprisingly quickly. After one weekend of marking up and styling, I had most of it ready to go. Then I spent a while tweaking. The source files are on Github.

I’m pretty happy with the end result. I’ll write a bit more about some of the details over the next while—the typography, the offline functionality, print styles, and stuff like that. In the meantime, I hope you’ll peruse this little book at your leisure…

Resilient Web Design.

If you like it, please spread the word.

Starting out

I had a really enjoyable time at Codebar Brighton last week, not least because Morty came along.

I particularly enjoy teaching people who have zero previous experience of making a web page. There’s something about explaining HTML and CSS from first principles that appeals to me. I especially love it when people ask lots of questions. “What does this element do?”, “Why do some elements have closing tags and others don’t?”, “Why is it textarea and not input type="textarea"?” The answer usually involves me going down a rabbit-hole of web archeology, so I’m in my happy place.

But there’s only so much time at Codebar each week, so it’s nice to be able to point people to other resources that they can peruse at their leisure. It turns out that’s it’s actually kind of tricky to find resources at that level. There are lots of great articles and tutorials out there for professional web developers—Smashing Magazine, A List Apart, CSS Tricks, etc.—but no so much for complete beginners.

Here are some of the resources I’ve found:

  • MarkSheet by Jeremy Thomas is a free HTML and CSS tutorial. It starts with an explanation of the internet, then the World Wide Web, and then web browsers, before diving into HTML syntax. Jeremy is the same guy who recently made CSS Reference.
  • Learn to Code HTML & CSS by Shay Howe is another free online book. You can buy a paper copy too. It’s filled with good, clear explanations.
  • Zero to Hero Coding by Vera Deák is an ongoing series. She’s starting out on her career as a front-end developer, so her perspective is particularly valuable.

If I find any more handy resources, I’ll link to them and tag them with “learning”.

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.

The road to Indie Web Camp LA

After An Event Apart San Francisco, which was—as always—excellent, it was time for me to get to the next event: Indie Web Camp Los Angeles. But I wasn’t going alone. Tantek was going too, and seeing as he has a car—a convertible, even—what better way to travel from San Francisco to LA than on the Pacific Coast Highway?

It was great—travelling through the land of Steinbeck and Guthrie at the speed of Kerouac and Springsteen. We stopped for the night at Pismo Beach and then continued on, rolling into Santa Monica at sunset.

Half Moon Bay. Roadtripping with @t. Pomponio beach. Windswept. Salinas. Refueling. Driving through the Californian night. Pismo Beach. On the beach. On the beach with @t. Stopping for a coffee in Santa Barbara. Leaving Pismo Beach. Chevron. Santa Barbara steps. On the road. Driving through Malibu. Malibu sunset. Sun worshippers. Sunset in Santa Monica.

The weekend was spent in the usual Indie Web Camp fashion: a day of BarCamp-style discussions, followed by a day of hacking on our personal websites.

I decided to follow on from what I did at the Brighton Indie Web Camp. There, I made a combined tag view—a way of seeing, for example, everything tagged with “indieweb” instead of just journal entries tagged with “indieweb” or links tagged with “indieweb”. I wanted to do the same thing with my archives. I have separate archives for my journal, my links, and my notes. What I wanted was a combined view.

After some hacking, I got it working. So now you can see combined archives by year, month, and day (I managed to add a sparkline to the month view as well):

I did face a bit of a conundrum. Both my home page stream and my tag pages show posts in reverse chronological order, with the newest posts at the top. I’ve decided to replicate that for the archive view, but I’m not sure if that’s the right decision. Maybe the list of years should begin with 2001 and end with 2016, instead of the other way around. And maybe when you’re looking at a month of posts, you should see the first posts in that month at the top.

Anyway, I’ll live with it in reverse chronological order for a while and see how it feels. I’m just glad I managed to get it down—I’ve been meaning to do it for quite a while. Once again, I’m amazed by how much gets accomplished when you’re in the same physical space as other helpful, motivated people all working on improving their indie web presence, little by little.

Greetings from Indie Web Camp LA. Indie Web Camping. Hacking away. Day two of Indie Web Camp LA.

A decade on Twitter

I wrote my first tweet ten years ago.

That’s the tweetiest of tweets, isn’t it? (and just look at the status ID—only five digits!)

Of course, back then we didn’t call them tweets. We didn’t know what to call them. We didn’t know what to make of this thing at all.

I say “we”, but when I signed up, there weren’t that many people on Twitter that I knew. Because of that, I didn’t treat it as a chat or communication tool. It was more like speaking into the void, like blogging is now. The word “microblogging” was one of the terms floating around, grasped by those of trying to get to grips with what this odd little service was all about.

Twenty days after I started posting to Twitter, I wrote about how more and more people that I knew were joining :

The usage of Twitter is, um, let’s call it… emergent. Whenever I tell anyone about it, their first question is “what’s it for?”

Fair question. But their isn’t really an answer. You send messages either from the website, your mobile phone, or chat. What you post and why you’d want to do it is entirely up to you.

I was quite the cheerleader for Twitter:

Overall, Twitter is full of trivial little messages that sometimes merge into a coherent conversation before disintegrating again. I like it. Instant messaging is too intrusive. Email takes too much effort. Twittering feels just right for the little things: where I am, what I’m doing, what I’m thinking.

“Twittering.” Don’t laugh. “Tweeting” sounded really silly at first too.

Now at this point, I could start reminiscing about how much better things were back then. I won’t, but it’s interesting to note just how different it was.

  • The user base was small enough that there was a public timeline of all activity.
  • The characters in your username counted towards your 140 characters. That’s why Tantek changed his handle to be simply “t”. I tried it for a day. I think I changed my handle to “jk”. But it was too confusing so I changed it back.
  • We weren’t always sure how to write our updates either—your username would appear at the start of the message, so lots of us wrote our updates in the third person present (Brian still does). I’m partial to using the present continuous. That was how I wrote my reaction to Chris’s weird idea for tagging updates.

I think about that whenever I see a hashtag on a billboard or a poster or a TV screen …which is pretty much every day.

At some point, Twitter updated their onboarding process to include suggestions of people to follow, subdivided into different categories. I ended up in the list of designers to follow. Anil Dash wrote about the results of being listed and it reflects my experience too. I got a lot of followers—it’s up to around 160,000 now—but I’m pretty sure most of them are bots.

There have been a lot of changes to Twitter over the years. In the early days, those changes were driven by how people used the service. That’s where the @-reply convention (and hashtags) came from.

Then something changed. The most obvious sign of change was the way that Twitter started treating third-party developers. Where they previously used to encourage and even promote third-party apps, the company began to crack down on anything that didn’t originate from Twitter itself. That change reflected the results of an internal struggle between the people at Twitter who wanted it to become an open protocol (like email), and those who wanted it to become a media company (like Yahoo). The media camp won.

Of course Twitter couldn’t possibly stay the same given its incredible growth (and I really mean incredible—when it started to appear in the mainstream, in films and on TV, it felt so weird: this funny little service that nerds were using was getting popular with everyone). Change isn’t necessarily bad, it’s just different. Your favourite band changed when they got bigger. South by Southwest changed when it got bigger—it’s not worse now, it’s just very different.

Frank described the changing the nature of Twitter perfectly in his post From the Porch to the Street:

Christopher Alexander made a great diagram, a spectrum of privacy: street to sidewalk to porch to living room to bedroom. I think for many of us Twitter started as the porch—our space, our friends, with the occasional neighborhood passer-by. As the service grew and we gained followers, we slid across the spectrum of privacy into the street.

I stopped posting directly to Twitter in May, 2014. Instead I now write posts on my site and then send a copy to Twitter. And thanks to the brilliant Brid.gy, I get replies, favourites and retweets sent back to my own site—all thanks to Webmention, which just become a W3C proposed recommendation.

It’s hard to put into words how good this feels. There’s a psychological comfort blanket that comes with owning your own data. I see my friends getting frustrated and angry as they put up with an increasingly alienating experience on Twitter, and I wish I could explain how much better it feels to treat Twitter as nothing more than a syndication service.

When Twitter rolls out changes these days, they certainly don’t feel like they’re driven by user behaviour. Quite the opposite. I’m currently in the bucket of users being treated to new @-reply behaviour. Tressie McMillan Cottom has written about just how terrible the new changes are. You don’t get to see any usernames when you’re writing a reply, so you don’t know exactly how many people are going to be included. And if you mention a URL, the username associated with that website may get added to the tweet. The end result is that you write something, you publish it, and then you think “that’s not what I wrote.” It feels wrong. It robs you of agency. Twitter have made lots of changes over the years, but this feels like the first time that they’re going to actively edit what you write, without your permission.

Maybe this is the final straw. Maybe this is the change that will result in long-time Twitter users abandoning the service. Maybe.

Me? Well, Twitter could disappear tomorrow and I wouldn’t mind that much. I’d miss seeing updates from friends who don’t have their own websites, but I’d carry on posting my short notes here on adactio.com. When I started posting to Twitter ten years ago, I was speaking (or microblogging) into the void. I’m still doing that ten years on, but under my terms. It feels good.

I’m not sure if my Twitter account will still exist ten years from now. But I’m pretty certain that my website will still be around.

And now, if you don’t mind…

I’m off to grab some lunch.


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.


My site has been behaving strangely recently. It was nothing that I could put my finger on—it just seemed to be acting oddly. When I checked to see if everything was okay, I was told that everything was fine, but still, I sensed something that was amiss.

I’ve just realised what it was. Last week on the 30th of September, I didn’t do or say anything special. That was the problem. I had forgotten my blog’s anniversary.

I’m so sorry, adactio.com! Honestly, I had been thinking about it for all of September but then on the day, one thing led to another, I was busy, and it just completely slipped my mind.

So this is a bit late, but anyway …happy fifteenth anniversary to this journal!

We’ve been through a lot together in those fifteen years, haven’t we, /journal? Oh, the places we’ve been and the things we’ve seen!

I remember where we were on our tenth anniversary: Bologna. Remember we were there for the first edition of the From The Front conference? Now, five years on, we’ve just been to the final edition of that same event—a bittersweet occasion.

Like I said five years ago:

It has been a very rewarding, often cathartic experience so far. I know that blogging has become somewhat passé in this age of Twitter and Facebook but I plan to keep on keeping on right here in my own little corner of the web.

I should plan something special for September 30th, 2021 …just to make sure I don’t forget.