Supported types are: 1. Valid media types ("image/png", "audio/*", "✱/✱") 2. File extensions with a leading dot (".png") 3. "*" (.* as a pseudo file extension was confirmed to allow everything in file pickers of all three major browser engines) 4. File extensions WITHOUT a leading dot ("png") – unlike in browser APIs – for backward compatibility and in case something doesn't parse as a media type