This is a tool for working out what proportion of visitors to a web page will be able to use all of its features.
When you're considering using a new browser feature in a web app, you have to weigh up how many users will be excluded because their browser doesn't support it.
The answer to this question doesn't just depend on how many browsers support the feature: it also depends on what other features you're already using.
If a feature you're considering requires the same minimum versions as another feature you're using, there's no downside to using it.
Select all the features that your app already uses, either by clicking through the tree of features, or by searching for features by name.
The browser support table will show you which browsers support all of the selected features, and from which versions.
The status bar at the top of the page shows the percentage of all browsers, weighted by measured usage, that support the selected features.