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Joining forces on better browser compatibility in 2021

Written By published March 22, 2021

Over the past few years, Microsoft has partnered with a group of browser vendors and other industry stakeholders to identify and address the top sources of web developer pain through initiatives like the MDN Web Developer Needs Assessment (“Web DNA”), as well as through our own product approach with Microsoft Edge and our contributions to the Chromium project.

The Web DNA results for the last two years have consistently highlighted browser compatibility as one of the top challenges faced by developers, and follow up research in the MDN Browser Compatibility Report and other channels has helped hone that signal into five areas where browser compatibility is a particularly strong pain point: CSS Flexbox, CSS Grid, CSS position: sticky, the CSS aspect-ratio property, and CSS transforms.

We’re excited to join with Google, Igalia, and the broader web community in committing resources to a cross-browser effort called #Compat2021, with the goal of substantial improvements in each area.


For this project, our joint working group identified the focus areas above based on feature usage data, number of bugs (or number of stars/upvotes on a given bug) in each vendor’s tracking system, various survey feedback, CanIUse data, and test results from web-platform-tests.

We then split focus among the working group to focus on areas in respective implementations. For example, the Microsoft Edge team intends to contribute fixes to Chromium to pass 100% of CSS Grid tests this year and to support work to improve interop across browsers, as well as assisting with triage in web-platform-tests. You can learn more about each focus area, including current pass rates and some of the factors included in our prioritization, over at

Getting Involved

As we kick off this effort, we need your help making sure we catch the most important issues and getting the word out! If you are encountering compatibility issues in the areas listed above, please continue to file bugs in the appropriate tool (either via the “Send Feedback” tool in Microsoft Edge, or directly in the appropriate project: Chromium, Webkit, or Gecko).

You can follow the project’s progress on the Compat 2021 Dashboard on web-platform-tests, subscribe to the public mailing list for updates, or follow @MSEdgeDev on Twitter for the latest updates from our team.

We’re excited to participate in this initiative to make the web an even better place to build great experiences that work across browsers!