PWA. Progressive Web Apps. Frances Berriman and Alex Russell coined the term "progressive web apps" in 2015 with what I think is a seminal post "Progressive Web Apps: Escaping Tabs Without Losing Our Soul".
3 years later, we've come a long way. From a loose collection of technologies - Service Worker, Manifest, Add to Homescreen, Web Push - that were originally only implemented in one browser engine, to a brand that has started to stick across the industry with businesses and developers, and all of the major browser vendors implementing the majority of the 'PWA' stack.
We've now got app directories, tools that help us understand roughly how many PWA's there are in the wild, and a host of awesome case studies about the benefits of PWA. But what defines a PWA? Frances and Alex came up with this list of traits:
Responsive: to fit any form factor
Connectivity independent: Progressively-enhanced with Service Workers to let them work offline
App-like-interactions: Adopt a Shell + Content application model to create appy navigations & interactions
Fresh: Transparently always up-to-date thanks to the Service Worker update process
Safe: Served via TLS (a Service Worker requirement) to prevent snooping
Discoverable: Are identifiable as "applications" thanks to W3C Manifests and Service Worker registration scope allowing search engines to find them
Re-engageable: Can access the re-engagement UIs of the OS; e.g. Push Notifications
Installable: to the home screen through browser-provided prompts, allowing users to "keep" apps they find most useful without the hassle of an app store
Linkable: meaning they're zero-friction, zero-install, and easy to share. The social power of URLs matters.
Importantly, this description marked the moment where we were all a little clearer about how we wanted to see the web and we've got tools that helped us understand if our site is a 'PWA' or not. Alex went even further and defined some of the technical aspects that make a 'PWA' a PWA.
With the hyperbole of this post out of the way, why isn't everyone building these things? Well, it can be hard. Very hard. We are asking developers and businesses to do a lot. In some cases focusing on AppShell can be a complete re-architecture of a site, in other cases 'AppShell' isn't the correct architecture. And in many cases the value or narrative isn't always quite clear.
I've been fortunate enough to be able to speak directly to businesses and developers about their concerns building on the web, specifically things that I have heard businesses and developers say about PWA, are:
We've got our site... but we are also making a PWA.
— Many B2B sites we spoke (actually, I saw this a lot in India)
Interesting. Are they different? Frequently not, but PWA is a 'thing' they have heard about and it's another product to launch. Much like m.* sites were the mobile version of the desktop site, PWA's can be another thing they have to launch.
I've got a PWA. It just does Push notifications.
— Too many people.
Wah. That's not a PWA, that's just using a piece of technology that native apps have had.
I'm only building a blog... it's not a PWA
— Many bloggers we spoke to.
Hmmm. It's a clear case that we've not been able to articulate why it's important for content sites to make the move.
I don't care about making it installable.. I don't need a Service Worker.
— Many publishers we spoke to.
Huh. People associate App's with installs, and the thought that a site or experience must act like an App install turns some people off from the concept as a whole. In 2015 there was a very interesting discussion about carrots that I encourage you to disect.
I don't need an app on desktop. I just need users to click 'checkout'
— Many retailers we spoke to.
Ok. That's pretty clear. The value to a user or the business is not there, and it's enough to stop a business prioritizing the traits of a PWA.
Progressive Web Apps are just better sites.
— Many developers we speak to.
Actually I hear this a lot from a lot of great web developers.
I encourage you to check out the writings of Jeremy Keith who for a while has been pushing the 'PW' in PWA for a long time and in a recent talk has said something similar:
There's a common misconception that making a Progressive Web App means creating a Single Page App with an app-shell architecture. But the truth is that literally any website can benefit from the performance boost that results from the combination of HTTPS + Service Worker + Web App Manifest.
— Jeremy Keith. "Any Site can be a Progressive Web App"
My personal feeling is that everyone is really hung up on the A in PWA: 'App'. It's the success and failure of the branding of the concept; 'App' is in the name, 'App' is in the conscious of many users and businesses and so the associations are quite clear.
To be absolutely clear, myself and many others across our team pushed hard on the 'App' term in the context of PWA, specifically in relation to competing with Mobile native experiences. Andrew Betts' post had a good summary against our original positioning, and whilst I don't think we were wrong, we did miss a chance to help the wider story specifically around form-factors that were not so mobile centric.
I used to ask audiences this when we were talking about the Chrome Web Store. Is Gmail an app or a site? An App, that's Easy. Is Twitter an app or a site? An App.. is it? If I'm just reading content, it still feels like a web site. Is Wikipedia an app or site? A site, absolutely; is it though? As an editor it feels very much like a tool.
Ultimately, I don't think it actually matters too much if a site is an app or an app is a site. People can and do create everything on the web: 'apps', games, VR bobbins, retail stores or just traditional 'sites', and it could be for any specific use case - media, entertainment, publishing, utilities, commerce...
If you tease apart the original definition of PWA, with the exception of 'installability' (see 'bag of carrots'), I don't think anybody could argue that if a developer improves their site in any one of the points Alex referenced then users get a better experience, and when user's get a better experience they value the web more and more people have a meaningful engagement with the web and keep using the web.
So how can we apply the PWA narrative in a way that every business and developer knows what they should focus on?
I've been thinking of a slight pivot based on the challenges we've seen in the industry, and I've tried to prioritize the importance of where developers and businesses can focus their efforts. (Note: I might channel BizKin)
We want businesses and developers to succeed by leveraging the web’s unique capabilities that allow them to: Reach the most users they can at the click of a button; Retain their users by bringing their best experiences across devices with a single set of code; and to meaningfully engage with their users by building a direct and ownable relationship with them.
I've tried to articulate this as a set of principles that the user should feel when using the web. Your experience should be: DISCOVERABLE, SAFE, FAST, SMOOTH, RELIABLE, MEANINGFUL
- Make it Discoverable
- Enable users to find your experience. The web is made of links and pages. Ideally every page and state should have a deep-link so that anyone can be sent to it from any site, be it an aggregator, a message, an email or a billboard. Content should be served so that any renderer can read it.
- Make it Safe
- Users and content owners can trust experiences built on the web, protecting identity, confidentiality and data integrity.
- Make it Fast
- Once the user has the link to your site, then the instant they tap it they are in your experience and able to start using it irrespective of the network or device that the user has.
- Make it Smooth
- When users are on your site the experience is responsive and interactive to all user gestures. Animations feel smooth and crisp, feedback is instant, scrolling is silky, navigations are instant. Ideally if you think of the web performance in terms of RAIL, you are focusing on the 'RAI'.
- Make it Reliable
- Users of your site perceive as few interruptions as possible when faced with unreliable network or devices. The experience should work and be responsive wherever the user is.
- Make it Meaningful
- You must provide value and meet your user's needs through high-quality experiences that provide value. This can seem quite fluffy, but Dion Almaer described it well. The focus is really about your site solving a need for the user, be it entertainment, smoothing out a purchase, advancement of knowledge or quick completion of a task. It's all about the UX.
A modern experience that meets these principle goals of fast, reliable, safe and smooth. It becomes progressively more capable using modern APIs and highly discoverable by harnessing the reach of the open web and at the core of it. A PWA should naturally meet each of these "principle goals" based on user expectations and continues to build on the experience as more technologies and capabilities come in. But so should any modern experience on the web today....
Progressive Web Apps — Progressive Web All-the-things.
This is where I want to push PWA over the next year. What do you think?
Thanks to Harleen Batra.
I lead the Chrome Developer Relations team at Google.
We want people to have the best experience possible on the web without having to install a native app or produce content in a walled garden.
Our team tries to make it easier for developers to build on the web by supporting every Chrome release, creating great content to support developers on web.dev, contributing to MDN, helping to improve browser compatibility, and some of the best developer tools like Lighthouse, Workbox, Squoosh to name just a few.