LGTM1 On Tuesday, October 20, 2026 at 11:08:15 PM UTC+2 Chromestatus wrote:
> *Contact emails* > [email protected] > > *Explainer* > https://github.com/w3c/webtransport/issues/544 > https://github.com/w3c/webtransport/pull/574 > > *Specification* > https://w3c.github.io/webtransport/#web-transport-configuration > > *Summary* > Allows WebTransport applications to indicate how many incoming streams > they expect to have open at once. Constructor hints configure the initial > QUIC stream allowance, reducing the risk that a server that needs high > stream concurrency is blocked by the initial stream limit. > > *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* > Some WebTransport applications expect a server to open many streams at > once. If the initial QUIC stream allowance is too low, the server must wait > for more stream credit before opening additional streams, adding avoidable > latency or limiting the number of open streams. Constructor hints let the > application state its expected stream count when creating the connection, > so the browser can advertise an appropriate initial allowance. Values above > the required minimum are preserved; values below 100 do not reduce the > effective allowance because the specification requires clients to initially > permit at least 100 streams of each type. > > *Initial public proposal* > *No information provided* > > *TAG review* > This is a small incremental addition to an existing feature which is > already standardized. > > *TAG review status* > Not applicable > > *Goals for experimentation* > None > > *Risks* > > > *Interoperability and Compatibility* > Compatibility risk is low because this is an additive API. Existing sites > that do not use the new names are unaffected. Interoperability risk is low > to moderate: WebKit implements these specific members, while Firefox > supports WebTransport but does not currently expose them. > > *Gecko*: Positive (https://bugzilla.mozilla.org/show_bug.cgi?id=2007825) > Firefox > supports WebTransport, but not these two anticipated-incoming-stream > members. Implementation work is in progress, no shipping milestone is > announced. > > *WebKit*: Shipped/Shipping (https://commits.webkit.org/303419@main) > Implemented > in WebKit revision 303419@main and shipped in Safari 26.4, including Safari > on iOS. > > *Web developers*: Positive ( > https://github.com/web-platform-tests/interop/issues/1121) The Interop > 2026 WebTransport proposal received 28 positive reactions. Developers also > reported active WebTransport use and significant cross-engine differences. > > *Other signals*: > > *Ergonomics* > The constructor options are nullable unsigned-short hints and default to > null. The corresponding attributes expose the currently stored values. > [EnforceRange] rejects values outside the unsigned-short range. Values > below 100 remain visible through the attributes but cannot reduce the > effective initial stream allowance below the specification-required minimum. > > *Activation* > No permission or user activation is required beyond the existing > WebTransport requirements. A site opts in by supplying either constructor > option. > > *Security* > This does not grant a new capability or expose application data. It lets a > site request a bounded initial stream allowance for its existing > secure-context WebTransport connection. Stream credit does not eagerly > allocate all streams. > > *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. The change is additive and does not modify behavior for applications > that do not use the new options or attributes. The implementation uses the > existing cross-platform WebTransport connection stack. > > > *Debuggability* > The hints can be inspected through the JavaScript attributes. Existing > DevTools and NetLog support for WebTransport and QUIC remains applicable. > > *Will this feature be supported on all six Blink platforms (Windows, Mac, > Linux, ChromeOS, Android, and Android WebView)?* > Yes > > *Is this feature fully tested by web-platform-tests > <https://chromium.googlesource.com/chromium/src/+/main/docs/testing/web_platform_tests.md>?* > Yes > > https://wpt.fyi/results/webtransport/anticipated-concurrent-incoming-streams.https.any.html?label=experimental&label=master > > *Flag name on about://flags* > enable-experimental-web-platform-features > > *Finch feature name* > WebTransportAnticipatedConcurrentIncomingStreams > > *Rollout plan* > Will ship enabled for all users > > *Requires code in //chrome?* > False > > *Tracking bug* > https://issues.chromium.org/issues/565837025 > > *Availability expectation* > The API is part of the W3C WebTransport specification and is implemented > by WebKit/Safari. Firefox supports WebTransport but does not yet expose > these specific members. Cross-browser availability is expected to improve > as implementations converge on the current WebTransport specification. > > *Adoption expectation* > Adoption is expected among WebTransport applications whose servers need to > create more than the minimum number of streams concurrently, including > real-time communication, media, gaming, remote interaction, and multiplexed > application protocols. Broader adoption will follow overall WebTransport > usage. > > *Adoption plan* > No dedicated outreach campaign is planned. Adoption is expected through > WebTransport documentation, examples, and client/server library support. > > *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 151 > Shipping on Android 158 > DevTrial on Android 151 > 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 known for these constructor options or attributes. The wider > WebTransport specification continues to progress, but no known open issue > requires a breaking change to these members before launch. > > *Link to entry on the Chrome Platform Status* > https://chromestatus.com/feature/5089961022980096?gate=5533718100967424 > > 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]. To view this discussion visit https://groups.google.com/a/chromium.org/d/msgid/blink-dev/516c776b-5496-4a8a-afcb-475ab294ae7cn%40chromium.org.
