Trust no one! Harry enumerates the reason why you should be self-hosting your assets (and busts some myths along the way).
There really is very little reason to leave your static assets on anyone else’s infrastructure. The perceived benefits are often a myth, and even if they weren’t, the trade-offs simply aren’t worth it. Loading assets from multiple origins is demonstrably slower.
Less than 24 hours after I put the call out for a solution to this gnarly service worker challenge, Trys has come up with a solution.
This is a really clever technique from Scott that he unveiled at An Event Apart in Seattle. It uses a header sent by a service worker to distinguish between returning and new visitors—much neater than relying on a cookie. I’ve updated my service worker on The Session to use this technique now.
Harry breaks down cache-control headers into steps that even I can understand. I’ll be using this a reference for sure.
I’m going to have to read through this article by Jake a few times before I begin to wrap my head around this background fetch thing, but it looks like it would be perfect for something like the dConstruct Audio Archive, where fairly large files can be saved for offline listening.
Remember when I wrote about using push without notifications? Sebastiaan has written up the details of the experiment he conducted at Indie Web Camp Berlin.
Imagine a PWA podcast app that works offline and silently receives and caches new podcasts. Sweet. Now we need a permissions model that allows for silent notifications.
This just blew my mind! A fiendishly clever pattern that allows you to inline resources (like critical CSS) and cache that same content for later retrieval by a service worker.
Crazy clever!
Service Workers have such huge potential power, and I feel like we (developers on the web) have barely scratched the surface with what’s possible.
Needless to say, I couldn’t agree more!
Trys is thinking through some of the implicatons of service workers, like how we refresh stale content, and how we deal with slow networks—something that’s actually more of a challenge than dealing with no network connection at all.
There’s some good food for thought here.
I’m so excited to see how we can use Service Workers to improve the web.
A step-by-step walkthrough of a really useful service worker pattern: allowing users to save articles for offline reading at the click of a button (kind of like adding the functionality of Instapaper or Pocket to your own site).
A great post by Tim following on from the post by Eric I linked to last week.
Is a secure site you can’t access better than an insecure one you can?
He rightly points out that security without performance is exlusionary.
…we’ve made a move to increase the security of the web by doing everything we can to get everything running over HTTPS. It’s undeniably a vital move to make. However this combination—poor performance but good security—now ends up making the web inaccessible to many.
Security. Performance. Accessibility. All three matter.
This is a heartbreaking observation by Eric. He’s not anti-HTTPS by any stretch, but he is pointing out that caching servers become a thing of the past on a more secure web.
Can we do anything? For users of up-to-date browsers, yes: service workers create a “good” man in the middle that sidesteps the HTTPS problem, so far as I understand. So if you’re serving content over HTTPS, creating a service worker should be one of your top priorities right now, even if it’s just to do straightforward local caching and nothing fancier.
I remember Jason telling me about this weird service worker caching behaviour a little while back. This piece is a great bit of sleuthing in tracking down the root causes of this strange issue, followed up with a sensible solution.
“Ah, this is good news!”, I thought, reading this update about how service worker scripts won’t be cached.
And that was the moment when I realised what an utter nerd I had become.
It looks like this is landing in Chrome. The navigator.connection.type property will allow us to progressively enhance based on connection type:
A web application that makes use of a service worker to cache resources during installation might have different bundles of assets that it might cache: a list of crucial assets that are cached unconditionally, and a bundle of larger, optional assets that are only cached ahead of time when
navigator.connection.typeis'ethernet'or'wifi'.
There are potential security issues around fingerprinting that are addressed in this document.
You can use navigator.storage.estimate() to get a (vague) idea of how much space is available on a device for your service worker caches.
Finally, the answer to one of the two hard questions in computer science.
This is a free online video course recorded by Jake a couple of years back. It’s got a really good step-by-step introduction to service workers, delivered in Jake’s typically witty way. Some of the details are a bit out of date, and I must admit that I bailed when it got to IndexedDB, but I highly recommend giving this a go.
There’s also a free course on web accessibility I’m planning to check out.
A step-by-step guide to building progressive web apps. It covers promises, service workers, fetch, and cache, but seeing as it’s from Google, it also pushes the app-shell model.
This is a handy resource but I strongly disagree with some of the advice in the section on architectures (the same bit that gets all swoonsome for app shells):
Start by forgetting everything you know about conventional web design, and instead imagine designing a native app.
Avoid overly “web-like” design.
What a horribly limiting vision for the web! After all that talk about being progressive and responsive, we’re told to pretend we’re imitating native apps on one device type.
What’s really disgusting is the way that the Chrome team are withholding the “add to home screen” prompt from anyone who dares to make progressive web apps that are actually, y’know …webby.
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.