If you just got used to PWA becoming the latest buzz word, Google just invented TWA and allowed these web apps into the Play store. Is this the future?

Progressive Web Apps promise to make web apps less dependent on the web. I've never been sure that Progressive was the right term to use, but now we have another candidate. Google wants to call them Trusted Web Activities, TWAs. A TWA is essentially a PWA with some extra security. You can create one using JavaScript and HTML and, of course, to make offline use possible you need a service worker.

A TWA can run full screen in Android Chrome. It can also run in WebView inside an Android app. Because of their extra requirements, TWAs only work in Android KitKat or newer and require an up-to-date installation of Chrome.  If you run the app under Chrome you can customize the way it looks as a Custom Chrome Tab - another Chrome proprietary feature. If you choose to run in a WebView then there are limitations - notably you can't use web push notifications and background sync. You also cannot extract information from the TWA to the enclosing app. The only interaction is passing in a query string when it is first opened.

There is also the small matter that running under Chrome means that you can gain access to shared state with the website that the TWA is associated with. All-in-all running under Chrome seems the best option.

At the moment creating a TWA and getting it into the Play store isn't entirely straightforward.

The blog post states that:

All content in TWAs must comply with Play store policy including policies for payments in-app purchases and other digital goods.

App users expect a great experience on their device. To ensure the quality of experience TWAs must meet PWA installability criteria and load fast. Loading speed is measured using Lighthouse and web content in TWAs must achieve a performance score of 80. Lighthouse is an open-source, automated tool for auditing performance & progressive web apps and is useful both as a benchmark and to help you build better websites.
As with any Play app, additional quality criteria may apply in the future. Apps which fail to meet TWA quality requirements or Play store policy may be denied entry or delisted.

So no presure there then...

So are TWAs the way to go?

The big problem is that PWAs and TWAs still run under the browser sandbox and this means they cannot access the native API - for this you still need something like Cordova or Flutter. If your app is mainly web-oriented this may be a limitation you can live with. A bigger problem is that a PWA is cross platform a TWA on the other hand is Chrome. True the differences are small and you can make your TWA available as a PWA for Firefox, say, but it is regrettable that something that could be totally cross-platform isn't. There is also the matter that TWAs are accessed via the Play store with the usual 30% going to the Play store. Perhaps it is worth it or perhaps not.

• Ian Elliot is the author of  JavaScript Async in which he discusses Service Workers, as well as Just JavaScript: An Idiomatic Approach and Just jQuery: The Core UI 

More Information

Introducing a Trusted Web Activity for Android

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