Fido JS

This web page will run the Fido format identification tool (v1.4.1) on any file you give to it. It runs entirely in your browser, via Pyodide.

There's a different version of this page that runs Siegfried instead of Fido.

You could also try dragging a file on to Siegfried's anvil!, which is similar web service that works by sending your file to server that runs Siegfried on it.