This is the W3C attestation mode checker. It's a work-in-progress. Other checkers available:
This one uses WD-07 structures and the FIDO U2F Attestation Mode and is intended for Firefox 58.
To use this to test Web Authentication support in Firefox, do the following:
Relying Party ID to use. "bin.coffee" and "webauthn.bin.coffee" should be the only valid options.