WebRTC header extensions match the claimed engine family
Check id webrtc-extmap-engine-family
What an ordinary browser yields
Under a Chrome UA, the SDP carries libwebrtc-shaped extensions including a webrtc.org experiment URI, and no Gecko-only csrc-audio-level.
What a detector infers
This check generates an SDP offer and collects its a=extmap RTP header-extension URIs. Those URIs are compiled into the WebRTC stack itself: libwebrtc (Chromium) ships webrtc.org/experiments/rtp-hdrext experiment URIs that Gecko never carries, and Gecko ships csrc-audio-level. Unlike codec lists, this set does not vary with the GPU or the host, which is what makes it a stable engine-family signal. Scoring applies only when the UA matches Chrome/<digits> and the runtime is Blink; under that claim, two conditions are flagged — the presence of Gecko-only csrc-audio-level, and the absence of any libwebrtc experiment extension. Either indicates a Chrome UA presented over a WebRTC stack from a different engine family. The comparison is family-level only; no per-milestone extension set is asserted, because Finch gating makes two identical stock Chromes differ. Severity is warn. A non-Chrome UA, or WebRTC being unavailable or disabled, yields N/A — the code notes that this is an environment fact, not a finding.
How to resolve it
Present a UA that matches the WebRTC stack you actually run. Don't put a Chrome UA over Gecko's WebRTC — the RTP header-extension set is compiled into the WebRTC stack, so unlike codec lists it doesn't vary with the GPU or the host. Only the engine family is asserted here: the exact per-milestone set does move with Finch gating, so two stock Chromes of the same version can legitimately differ.
Nearby checks in Network & WebRTC
- host candidates use an mDNS hostname rather than a literal LAN address
webrtc-mdns-hostWhen WebRTC enumerates the ways a peer might reach you, it offers host candidates describing your machine's own network interfaces. - ICE gathering offers at least one candidate on a working network
webrtc-gathering-suppressedThe other WebRTC rows on this page read what the candidates SAY. - The WebRTC host candidate does not expose a routable public address
webrtc-address-classReading from the same fully offline RTCPeerConnection — built with no iceServers, so host-only gathering, no STUN, no packets — the first… - every server-reflexive candidate has a host candidate behind it
webrtc-srflx-without-hostA server-reflexive candidate is not an address the browser knows about itself. - The WebRTC SDP offer matches the engine the User-Agent claims
sdp-engine-signatureAn RTCPeerConnection is constructed with no iceServers key, which makes the probe entirely offline: the native stack builds a local SDP… - NetworkInformation is only present on Chromium engines
connection-api-vs-engineThis check compares an API's mere existence against the engine family named by the User-Agent. - navigator.connection.rtt obeys Chromium's 25ms quantisation
connection-rtt-quantizationThe probe reads navigator.connection.rtt from the NetworkInformation API, and the check runs only when that value is a number. - a slow effectiveType comes with a non-zero round-trip estimate
connection-ect-vs-rttnavigator.connection reports the link two ways that come from one estimator: effectiveType is a coarse bucket (slow-2g, 2g, 3g, 4g) and rtt…
Clearcote is a browser built for fingerprint coherence
It is a Chromium fork, maintained by the same people who wrote this reference. It ships as a compiled browser rather than as a stealth script injected into someone else's — which is a description of how it is built, and is not an argument about how it behaves on this check.
This audit takes no position on how Clearcote scores on Network & WebRTC checks, on this one, or anywhere else. It has no baseline corpus of other people's fingerprints to rank you against and no vendor scoreboard — nearly every check is self-referential, asking one browser the same question through two independent APIs and reporting whether both answers can be true at once. It runs identically on any browser, including ours. Run it on yours and read the result yourself.
See the other checks in Network & WebRTC — the family webrtc-extmap-engine-family belongs to.