Deprecated APIs are scheduled to be removed from Chrome. Calling these APIs after they're removed causes errors on your site.
How the Lighthouse deprecated API audit fails #
Lighthouse flags pages that call deprecated APIs:
Lighthouse includes all deprecated API warnings that Chrome logs to the DevTools Console.
How to remove deprecated APIs #
Go to Chrome Platform Status and expand the entries for the APIs that you're using to learn why the APIs are deprecated and how to replace them.