LGTM2 On Monday, October 12, 2026 at 11:40:41 AM UTC-7 [email protected] wrote:
> LGTM1; thanks for closing this gap. > > On Wednesday, October 7, 2026 at 10:23:27 AM UTC-7 Chromestatus wrote: > >> *Contact emails* >> [email protected] >> >> *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 >> <https://issues.chromium.org/issues?q=customfield1222907:%22Blink%3ENetwork%3EWebTransport%22> >> >> *Web Feature ID* >> webtransport <https://webstatus.dev/features/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 >> >> *TAG review* >> This is a small incremental implementation of attributes already defined >> in the existing W3C WebTransport specification. It does not introduce a new >> API design or Chromium-specific extension >> >> *TAG review status* >> Not applicable >> >> *Goals for experimentation* >> None >> >> *Risks* >> >> >> *Interoperability and Compatibility* >> Compatibility risk is low because both attributes are additive and do not >> change existing WebTransport behavior. Interoperability risk is low because >> the attributes and their "pending" , "reliable-only" , and >> "supports-unreliable" values are defined by the W3C WebTransport >> specification. Equivalent APIs are implemented or partially implemented in >> WebKit and Firefox, and WebTransport is an Interop 2026 focus area. >> >> *Gecko*: Shipped/Shipping ( >> https://bugzilla.mozilla.org/show_bug.cgi?id=1709355) >> >> *WebKit*: Shipped/Shipping (https://github.com/WebKit/WebKit/pull/55124) >> >> *Web developers*: Positive ( >> https://github.com/web-platform-tests/interop/issues/1121) The Interop >> 2026 WebTransport proposal received 28 👍 reactions. Developers also >> reported active WebTransport use and significant cross-engine differences. >> >> *Other signals*: >> >> *Ergonomics* >> Ergonomics risk is low. reliability synchronously returns "pending" >> while connecting, and applications can await WebTransport.ready before >> reading its final value. The static supportsReliableOnly attribute >> enables capability detection before creating a connection. >> >> *Activation* >> Activation risk is low. This is an additive API that does not change >> existing WebTransport behavior or require server changes. Developers can >> use standard feature detection and retain existing fallbacks for older >> browsers. >> >> *Security* >> No new network capability or sensitive information is exposed. The >> attributes report whether an implementation or session supports exclusively >> reliable or unreliable WebTransport, which is already observable through >> the available WebTransport APIs. They expose no server data, credentials, >> addresses, or user-specific information. >> >> *WebView application risks* >> >> Does this intent deprecate or change behavior of existing APIs, such that >> it has potentially high risk for Android WebView-based applications? >> Low. This is an additive API surface and does not modify the behavior of >> existing WebTransport connections. WebView applications that do not use the >> attributes are unaffected >> >> >> *Debuggability* >> The attributes can be inspected directly from JavaScript or the Chrome >> DevTools Console. Developers can inspect transport.reliability before and >> after transport.ready resolves and inspect >> WebTransport.supportsReliableOnly without creating a connection. No >> additional DevTools-specific support is required >> >> *Will this feature be supported on all six Blink platforms (Windows, Mac, >> Linux, ChromeOS, Android, and Android WebView)?* >> Yes >> All Blink platforms on which WebTransport is supported. The >> implementation is in cross-platform Blink code. >> >> *Is this feature fully tested by web-platform-tests >> <https://chromium.googlesource.com/chromium/src/+/main/docs/testing/web_platform_tests.md>?* >> Yes >> WPT coverage verifies that: • Initial "pending" state. • Transition >> after ready . • Web IDL exposure. Static attribute and initial state: >> https://wpt.fyi/results/webtransport/reliability.https.any.html?label=experimental&label=master&aligned >> >> State after connection establishment: >> https://wpt.fyi/results/webtransport/reliability.https.window.html?label=experimental&label=master&aligned >> >> IDL harness: >> https://wpt.fyi/results/webtransport/idlharness.https.sub.any.html?label=experimental&label=master&aligned >> >> *Flag name on about://flags* >> chrome://flags/#enable-experimental-web-platform-features >> >> *Finch feature name* >> WebTransportReliability >> >> *Rollout plan* >> Will ship enabled for all users >> >> *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* >> Shipping on desktop 158 >> DevTrial on desktop 155 >> Shipping on Android 158 >> DevTrial on Android 155 >> Shipping on WebView 158 >> >> *Anticipated spec changes* >> >> Open questions about a feature may be a source of future web compat or >> interop issues. Please list open issues (e.g. links to known github issues >> in the project for the feature specification) whose resolution may >> introduce web compat/interop risk (e.g., 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=5518510552907776 >> >> *Links to previous Intent discussions* >> Intent to Prototype: >> https://groups.google.com/a/chromium.org/d/msgid/blink-dev/6a9705af.b5ef4c6f.265fb1.0007.GAE%40google.com >> >> >> This intent message was generated by Chrome Platform Status >> <https://chromestatus.com>. >> > -- 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]. 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