What are they?

As described on MDN:

Progressive web apps involve taking standard web sites/apps that enjoy all the best parts of the Web — such as discoverability via search engines, being linkable via URLs, and working across multiple form factors — and supercharging them with modern APIs (such as Service Workers and Push and features that confer other benefits more commonly attributed to native apps.

PWA s are, in the simplest case, websites that register a Service Worker for offline support and contain a <link rel="manifest" /> to provide some basic app info. If both of these requirements are satisfied, the browser may show a badge or prompt to the user that enables the app being “installed.”

Isn’t this old news?

“So what? We’ve had offline solutions and fancy bookmarks before.”

For very simple apps, AppCache would do the job, yes. Well, it will for now, since it is now deprecated and support is expected to be dropped.

Browsers have also had “Add to Home Screen / Desktop” support as well. I can’t really say that PWAs are currently much more than an improvement on the interface and discoverability. I think discoverability is significantly better though, since supporting browsers will show a badge or prompt to install the app instead of relying on users knowing of and using the feature.

If you were to focus solely on these things, then I would agree that PWAs are not that big of a deal. But, Service Workers do more than just allow content to be available offline or on slow networks. They allow for notifications, background syncing, posting content while offline that is sent whenever the network becomes available again. They also allow for scripted control of their caches, allowing things such as users controlling what content is available offline.

PWAs are also more than any particular or fixed set of features. Rather, they are an evolving set of tools available for delivering better user experiences. And, just like Responsive Design is more than just declaring a <meta name="viewport" /> , PWAs merely begin with a better approach to what was already available.

Looking to the Future

The current hype you’ll see about PWAs focuses almost exclusively on Chrome on Android. This is, to be blunt about it, incredibly naive! Google may have been the bigest pusher of PWAs, and Chrome may have been the first browser to support much of the technology, but nothing about PWAs is exclusive to Chrome. Firefox 58 for Android will be enabling custom tabs and adding an “Add to Home Screen” badge. Safari and Edge are developing their implementations of Service Workers, and Edge is developing Web Application Manifest.

As you may have guessed by mention of Edge, PWAs are not exclusive to Android, or even mobile devices. Microsoft is planning on distributing them through the Windows Store. It’s easy to imagine that, in the near future, PWAs will be supported by either all major browsers, if not by Operating Systems. When this happens, which is all but a certainty at this point, we’ll finally be able to realize the dream to “write once; run everywhere.”

Right now, you may be thinking, “There’s no way something like PhotoShop would be usable as a PWA.” The battle of Web vs. Native has been fought for many years now and the popular opinion today is that web has lost, largely due to performance issues.

Have you heard of WebAssembly?

WebAssembly is a new type of code that can be run in modern web browsers — it is a low-level assembly-like language with a compact binary format that runs with near-native performance and provides languages such as C/C++ with a compilation target so that they can run on the web. It is also designed to run alongside JavaScript, allowing both to work together.

Now, imagine the possibilities of a PWA using WASM and other amazing new-ish APIs like:

And, for integrating with the OS to handle files or protocols, we could implement these using two methods that already exist that are under-utilized: