GitHub Pages supports more than 750 MIME types across 1,000s of file extensions. The list of supported MIME types is generated from the mime-db project, which aggregates MIME types from the Apache and Nginx projects as well as the official IANA list of internet content types.
MIME types are additional headers that servers send to provide browsers with information about the types of files being requested and how to handle the file once downloaded.
To add or modify MIME types for use on GitHub Pages, see the mime-db Contributing instructions.