Cross browser compatibility got a lot better in recent years. There is a huge set of browser APIs which work very very similar in all modern browsers. The implementations are so close that many of the CLIs that come with todays frontend frameworks set up tests that only run in one browser or no browser at all.

But unfortunately things are still very different when it comes to media APIs. There are a lot of APIs which are still new and work in progress. They often don't work as promised by the specifications and they often work differently from browser to browser or they don't work at all. It's not uncommon to run into a browser bug.

Reporting a bug is the mandatory first step to get it fixed. And therefore it's best to have a reproducible test case which demonstrates the bug. Creating this test case is often the tricky part. But once it's done it can also be turned into a Web Platform Test.

Web Platform Tests are a set of tests that verify browser implementations. All big browser vendors got together to create a large corpus of tests that they run across all browsers. The results are used often to show off spec compatibility. Web Platform Tests are for example used by the yearly Interop projects. But it's an open source project. Anyone can contribute a test.

Adding your test ensures visibility. It will lower the compatibility score if it fails. It will probably also increase the motivation to get it fixed. And last but not least it will make sure that the same bug never pops up again in any of the tested browsers.

Let's improve browser compatibility together one test at a time.