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Explainer https://github.com/w3c/webtransport/blob/main/explainer.md#transport-modes Specification https://www.w3.org/TR/webtransport/#dom-webtransport-reliability Summary Adds the WebTransport.reliability instance attribute and static WebTransport.supportsReliableOnly attribute. These APIs indicate whether the user agent supports WebTransport over exclusively reliable connections and whether an established session supports unreliable transport such as datagrams. In Chromium, reliability initially returns "pending" and changes to "supports-unreliable" after an HTTP/3 WebTransport connection is established. Since Chromium does not currently support HTTP/2 fallback, WebTransport.supportsReliableOnly returns false; any successfully established session uses HTTP/3 and supports unreliable datagrams. Blink component Blink>Network>WebTransport Web Feature ID webtransport Motivation WebTransport may operate over connections with different reliability capabilities. Applications such as games, interactive media, and real-time collaboration tools need to know whether unreliable datagrams are available before selecting their transport strategy. WebTransport.supportsReliableOnly reports whether the user agent supports WebTransport over exclusively reliable connections. The per-session reliability attribute is "pending" while connecting and becomes "reliable-only" or "supports-unreliable" once the transport is known. Chromium currently implements WebTransport over HTTP/3 with unreliable datagram support, so established sessions report "supports-unreliable" and supportsReliableOnly returns false. Initial public proposal https://github.com/w3c/webtransport/pull/385 Goals for experimentation None Requires code in //chrome? False Tracking bug https://issues.chromium.org/issues/545636884 Measurement Measure through Web Platform Test results, Interop 2026 WebTransport results, and developer feedback. No dedicated UMA metric is planned because this is an additive capability-reporting API that does not change network behavior. Availability expectation Expected to become available across major browser engines as part of the W3C WebTransport specification. WebKit implements both attributes, while Firefox currently implements the per-session reliability attribute Adoption expectation Expected to be adopted by WebTransport applications that use datagrams or need to operate across transports with different reliability capabilities. Adoption plan Adoption is expected to happen organically as WebTransport applications use these attributes to select between reliable streams and unreliable datagrams. Non-OSS dependencies Does the feature depend on any code or APIs outside the Chromium open source repository and its open-source dependencies to function? No Estimated milestones No milestones specified Anticipated spec changes Open questions about a feature may be a source of future web compat or interop issues. Please list open issues (eg links to known github issues in the project for the feature specification) whose resolution may introduce web compat/interop risk (eg, changing to naming or structure of the API in a non-backward-compatible way). None. The attributes and WebTransportReliabilityMode values are already defined in the W3C WebTransport specification. Link to entry on the Chrome Platform Status https://chromestatus.com/feature/5094058497277952?gate=6222197994684416 This intent message was generated by Chrome Platform Status. -- You received this message because you are subscribed to the Google Groups "blink-dev" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion visit https://groups.google.com/a/chromium.org/d/msgid/blink-dev/6a9705af.b5ef4c6f.265fb1.0007.GAE%40google.com.
