Ready for Developer Testing: Local network access restrictions for WebTransport

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Nov 24, 2025, 11:04:56 AM (3 days ago) Nov 24
to blin...@chromium.org, hc...@chromium.org
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Explainer
https://github.com/WICG/local-network-access/blob/main/explainer.md

Specification
https://wicg.github.io/local-network-access/#integration-with-webtransport

Summary
Restricts the ability to make requests to the user's local network using WebTransport, gated behind a permission prompt. A local network request is any request from a public website to a local IP address or loopback, or from a local website (e.g. intranet) to loopback. Gating the ability for websites to perform these requests behind a permission reduces the ability of sites to use these requests to fingerprint the user's local network. This permission is restricted to secure contexts. This work is adding to the Local Network Access Restrictions work here: https://chromestatus.com/feature/5152728072060928

Blink component
Blink>SecurityFeature>LocalNetworkAccess

Web Feature ID
local-network-access

Risks


Interoperability and Compatibility
No information provided

Gecko: No signal

WebKit: No signal

Web developers: No signals

Other signals:

Activation
A new permission will be shown to users, which may be unexpected, and if users deny the permission functionality may break (potentially requiring additional support from site owners). As this is building off of the first Local Network Access launch, this should be a minimal risk, but has a chance of impacting those who are impacted by this launch but were not impacted by the original Local Network Access launch. This is slightly different from the other LNA launches as WebTransport is restricted to secure contexts, so we do not have any worries about mixed content blocking.

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?

No information provided


Debuggability
No information provided

Will this feature be supported on all six Blink platforms (Windows, Mac, Linux, ChromeOS, Android, and Android WebView)?
No
This is unsupported on WebView for the same reasons that Local Network Access is unsupported on WebView

Is this feature fully tested by web-platform-tests?
No


DevTrial instructions
https://docs.google.com/document/d/1GHbpRTCnfDXq9o8WKyrG7oPAiWC6Yozac-PvbfO3KoY/edit?usp=sharing

Flag name on about://flags
local-network-access-check-webtransport

Finch feature name
LocalNetworkAccessChecksWebTransport

Requires code in //chrome?
False

Tracking bug
https://issues.chromium.org/issues/421216834

Estimated milestones
DevTrial on desktop144
DevTrial on Android144


Link to entry on the Chrome Platform Status
https://chromestatus.com/feature/5126430912544768

Links to previous Intent discussions
Intent to Prototype: https://groups.google.com/a/chromium.org/d/msgid/blink-dev/68cc4140.2b0a0220.28e063.0124.GAE%40google.com


This intent message was generated by Chrome Platform Status.
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