Browser Compat Data - developer gold

Every year developers tell us that Web Compat is their top developer frustration. It's great to see my team spin up projects like Compat 2021 which help address the pain points developers have day to day, but is the situation getting better?

I have lots of questions about the state of the web.

  • What was the latest browser versions at the end of 2020 and what APIs did they have?
  • What APIs can I use if I target WebKit, Gecko and Blink?
  • What APIs are in Safari, but not in Blink? i.e, What is in X but not in Y?
  • How compatible is the web?
  • etc.

I'm dedicating a lot of my time and my teams time to helping improve Compatibility and answering these questsions. I know it's the correct thing to do, but at some point you have to justify you and your teams investments. I'm currently in that phase, and I'm deep in the weeds of trying to understand if broadly the web is becoming more compatible.

I think web is getting more compatible... but, I don't actually know if it is. Is it an incorrect perception? Is my thesis about the lumpy web correct? We need data.

Since the Lumpy Web post, a lot more data is available to Web Developers and I am hoping that this post can shine some light on the work being done to help us all understand the shape of the web platform.

https://caniuse.com is awesome and it's still the primary resource for many web developers when understanding the web. It's an incredible tool that let's you quickly search for an API and see if you feel comfortable using it given it's level of support. It even has data available for you to query - I've build tools that use's it's data (I want to use). I don't envy Alexis though, it's incredibly hard to keep up to date 1) Because the web platform is massive, and 2) it changes frequently with additions and removals of APIs.

There is one true source of Web Compat data, at least as I understand it: Web Platform Tests (https://wpt.fyi/). Web Platform Tests is a common test suite that is run across a range of browsers and it let's you see if the engines are broadly conforming to what is described in the Specs.

I've spent a lot of time looking at wpt.fyi and it's incredible. The test suite is huge (it even has it's own query language), but it's not really meant for the typical web developer. It's intended use is for the creators of Browser Engines to help them see where they are as compared to other browsers.

It turns out that Mozilla created a middle-ground: Something between the raw data needed for caniuse and a comprehensive but consumable view of the data from WPT called "Browser Compat Data"(BCD). The MDN team did a lot of the heavy lifting to work out the browser support for each API and integrate it into MDN compatibility tables.

The project is active too, with a lot of work done by the Open Web Docs team and includes a comprehensive Governance model. Even better, the data is accessible.

Wouldn't it be great if you could query that data? It turns out you can. BCD has an NPM module that contains all that data which can be unpakaged like so const response = await fetch("https://unpkg.com/@mdn/browser-compat-data@3.3.7/data.json");.

Using this data, I built a simple of Demo: The Web Of ... (Source) - For any given date it will work out what was the latest browser versions, and then for your preferred set of browsers (i.e, Chrome, Safari, Firefox etc) will let you pick an area of the web platform you care about the most (APIs, HTML, CSS etc.) and see which APIs are available in all of those browsers.

The web of web site.

The idea of this app is to give you an idea of what API's are available for you to use without polyfill for the target browsers you need to support.

This is just one example of what is possible once you have the data at your finger tips. The source code is here.

Once we have the data that describes the state of the web, we have the ability to ask questions that we've never been able to get answers to. We could finally have a score akin to SpeedIndex that instead describes Web Compat, a CompatIndex if you like. But even before that, this data will be useful for developers every single day. I'd love to see more tools such as Chrome DevTools integrate this data to help developers quickly understand how well supported their sites will be.

So, can we answer the following questions?

  • What was the latest browser versions at the end of 2020 and what APIs did they have? - Yes. Check out https://the-web-of.glitch.me, it finds the latest browser before a given date, then for each API see's if that browser supported it.
  • What APIs can I use if I target WebKit, Gecko and Blink? - Yes, see the above, but only select those browsers.
  • What APIs are in Safari, but not in Blink? i.e, What is in X but not in Y? - Yes, you could do this. Filter all the API's in Safari, then remove each API that Blink has.
  • How compatible is the web? Yes - We first need a metric, but we can compare each browser against every other browser and see where the gaps in compatibility are and use that as a percentage, you could even do it with a subset of browsers.

Please take a look at the BCD project, and if you can, help out.


Vinyl. If you are reading this, thank you for all the amazing work you have been doing.

About Me: Paul Kinlan

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.