WebAuthn Compat Notes

A document to track more specific nuances than https://caniuse.com/?search=webauthn

macOS

Functionality	Links	Chrome	Firefox	Safari
`residentKey` in `authenticatorSelection`	spec	✅ 109.0.5414.87	❌ 111.0a1	✅ 16.2
`PublicKeyCredential.isConditionalMediationAvailable()`	spec, crbug	✅ 109.0.5414.87	❌	✅ 16+
`largeBlob` extension	spec, crbug, chromestatus	🏁¹²	❌³	❌³
`authenticatorAttachment` on `PublicKeyCredential` return values	spec	✅ 109.0.5414.87	❌ 111.0a1	✅ 16.2
`parseCreationOptionsFromJSON` and `parseRequestOptionsFromJSON` on `globalThis.PublicKeyCredential`	spec, crbug, bugzilla	❌ 109.0.5414.87	❌ 111.0a1	❌ 16.2
Methods on `AuthenticatorAttestationResponse`: `getAuthenticatorData`, `getPublicKey`, `getPublicKeyAlgorithm`, `getTransports`	spec	✅ 109.0.5414.87	❌ 111.0a1	✅ 16.2
Conditional mediation with allowlist	spec PR	TODO	TODO	TODO

✅ Fully implemented and available without a custom setting/flag.
🏁 Fully implemented and available only with a custom setting/flag.
🚧 Partially implemented or implementation drafted (may or may not be behind a flag).
❌ Unimplemented

Look up what Chrome versions a commit is in: https://omahaproxy.appspot.com/ ("Find Releases")

Flag: chrome://flags/#enable-experimental-web-platform-features ↩
Works with a YubiKey Bio but not Touch ID. ↩
Completely ignores the largeBlob extensions (e.g. doesn't fail when passed largeBlob: {support: "required"}) ↩ ↩²