WebTransport Datagram readable stream type

Category: Network / Connectivity
Type: Chromium catches up
Status: Proposed (Chrome Proposed)
Intent stage: None

Breaking change: No
Enterprise impact: None
Chromium flag: chrome://flags/#enable-experimental-web-platform-features
Spec maturity: Published standard
Web Platform Tests: Yes

WPT details: https://wpt.fyi/results/webtransport/datagrams.https.any.html?label=experimental&label=master&aligned

Summary

Adds the WebTransportOptions.datagramsReadableType constructor option. By default, incoming WebTransport Datagrams are exposed through a default ReadableStream . Applications that require BYOB reading can request a readable byte stream by setting datagramsReadableType: "bytes" .

Motivation

WebTransport Datagrams are discrete messages rather than an undifferentiated byte sequence. A readable byte stream can lose empty Datagrams and can lose message boundaries when BYOB reads use a minimum byte count spanning multiple Datagrams. Making a default ReadableStream the default preserves Datagram boundaries and empty Datagrams. Applications that benefit from BYOB allocation control can explicitly opt into the byte-stream behavior.

Standards & signals

Specification: https://www.w3.org/TR/webtransport/#dom-webtransportoptions-datagramsreadabletype
Firefox: Positive — Firefox is implementing datagramsReadableType: "bytes" and BYOB Datagram reads
Safari: In development — WebKit main implements the standardized datagramsReadableType option
Web developers: Positive — The Interop 2026 WebTransport proposal received 28 👍 reactions. Developers also reported active WebTransport use and significant cross-engine differences.
Tracking bug: https://issues.chromium.org/issues/547572475

Ecosystem

Web Platform Tests: https://wpt.fyi/results/?q=webtransport%2Fdatagrams
Chrome Platform Showcase: https://chrome-platform-showcase.paulkinlan-ea.deno.net/features
GenDN reference: https://gendn.paulkinlan-ea.deno.net/features
chrome.dev demos search: https://www.google.com/search?q=site%3Achrome.dev+WebTransport%20Datagram%20readable%20stream%20type
MDN Web Docs: https://developer.mozilla.org/en-US/search?q=WebTransport%20Datagram%20readable%20stream%20type
Baseline status: https://webstatus.dev/?q=WebTransport%20Datagram%20readable%20stream%20type

Explainers: https://github.com/w3c/webtransport/blob/main/explainer.md

View on chromestatus.com