WebRTC Diagnostic Logging API

at a glance

Syntax

The API is exposed as a set of static methods on the RTCPeerConnection interface — synchronous calls, not the promise-returning navigator.rtc surface of the earlier draft. IDL from the WebRTC Extensions specification:

[Exposed=Window]
partial interface RTCPeerConnection {
  static DOMString startDiagnosticLogging(optional RTCDiagnosticLoggingOptions options = {});
  static undefined stopDiagnosticLogging();
  static undefined cancelDiagnosticLogging();
};

dictionary RTCDiagnosticLoggingOptions {
  record<DOMString, DOMString> metadata;
};

startDiagnosticLogging(options)

Begins a logging session. The user agent starts recording internal WebRTC logs, and the call returns a unique session ID (a UUID) — the only piece of diagnostic information the application ever receives. There is no promise: the returned string is the session ID. The session lives in an [[RTCDiagnosticLoggingSessionId]] internal slot on the relevant global object, which the specification initializes to null. (The W3C WebRTC Extensions specification is internally inconsistent about where this slot lives: its Internal slots section defines it on the relevant global object, while its algorithm steps reference RTCPeerConnection/[[RTCDiagnosticLoggingSessionId]]; this page follows the Internal slots definition.)

stopDiagnosticLogging()

Ends the session and finalizes the log file. The user agent must not log WebRTC activity for the session afterwards. The call returns undefined; whether the finalized log is ever shared with the browser vendor is a matter of user authorization and user-agent behaviour, not of an API switch.

cancelDiagnosticLogging()

Stops the session and discards everything collected; the user agent must not log afterwards, and because the data is discarded it cannot be shared. The call returns undefined. Two naming mismatches are worth knowing about, and neither changes what you call: the WICG incubation document's section heading for this operation reads discardDiagnosticLogging() while its IDL — the authoritative surface, and what implementers type — declares cancelDiagnosticLogging() (the W3C specification has no discardDiagnosticLogging anywhere); and the explainer's example code uses cancelLogging(). The explainer also still names the second operation finishDiagnosticLogging() where the IDL says stopDiagnosticLogging().

What the app can and cannot see

The design deliberately keeps diagnostic content away from the application. The explainer states as an explicit non-goal that the API exposes nothing to the app beyond the session ID — the logs may contain internal information about user activity. The finished log is stored as a local file that the user can access, and any share path gives it to the user agent (the browser vendor) — never to the site. The format of the log and the mechanism by which it may be shared are intentionally unspecified; the only hard requirement is explicit user authorization. A site can attach small pieces of metadata (for example an app identifier) so a shared log can be matched to a bug report filed with the browser vendor.

Examples

// Before starting a call — begin a session (metadata only: <= 5 pairs, <= 100 chars each)
const sessionId = RTCPeerConnection.startDiagnosticLogging({
  metadata: { app: "my-call-app" },
});   // synchronous: DOMString, not a promise
// The app stores the session ID — it is the ONLY data it ever gets back.

// When the call ends normally — finalize the log locally
RTCPeerConnection.stopDiagnosticLogging();

// When the captured session is not useful — discard it entirely
RTCPeerConnection.cancelDiagnosticLogging();

Browser compatibility

There is no browser-compat-data (BCD) entry for this API yet, so the table below is an interim view built from ChromeStatus ship data and public signals — not from BCD.

Beyond vendor signals, the explainer records stakeholder positions: Google (implementer) positive, and ByteDance positive (as a WebRTC application stakeholder, not a browser vendor).

Specifications

See also

• WICG — WebRTC Diagnostic Logging explainer
• W3C WebRTC Extensions — Diagnostic Logging
• W3C webrtc-extensions proposal — diagnostic logging
• Chrome origin trials — registration
• Chrome Platform Showcase — WebRTC Diagnostic Logging API (still on the pre-rewrite surface as of 2026-10-06; also: capability & policy probe, bug-report companion)