Contact emails

[email protected]

Specification

https://github.com/w3c-fedid/FedCM/pull/760

Summary
To address cross-site identity correlation risks in the FedCM API, Identity 
Providers (IdPs) that utilize client_metadata within their FedCM 
configuration are required to implement the direct endpoints format in the 
.well-known/web-identity file. This mandate ensures that both 
accounts_endpoint and login_url are explicitly defined whenever a 
client_metadata_endpoint is present. This approach strengthens privacy 
protections by preventing relying parties from exploiting metadata to 
correlate user identities across multiple sites. For further details and 
discussion, refer to https://github.com/w3c-fedid/FedCM/issues/700.

Migration Plan
Chrome will enforce this rule in two phases:

Chrome 143 (Warning Phase): If client_metadata_endpoint exists but 
accounts_endpoint or login_url is missing, the browser will display console 
warnings. This gives IdPs time to update configurations.

Chrome 145 (Enforcement Phase): The requirement becomes mandatory. FedCM 
configurations missing these endpoints will be blocked, preventing 
authentication flows.


Blink component

Blink>Identity>FedCM


<https://issues.chromium.org/issues?q=customfield1222907:%22Blink%3EIdentity%3EFedCM%22>

Web Feature ID

fedcm


<https://webstatus.dev/features/fedcm>

TAG review

None


Risks

Interoperability and Compatibility

IdPs failing to update .well-known/web-identity for FedCM client metadata 
risk breaking authentication flows. Chrome 143 issues warnings, but 
starting Chrome 145, missing accounts_endpoint or login_url will block 
configurations entirely. Immediate migration is critical to maintain 
compatibility and avoid service disruptions for relying parties and 
end-users.

Gecko: No signal (Firefox does not wish to support the client metadata 
endpoint of the FedCM API so this would not be a change applicable to them)

WebKit: No signal

Web developers: No signals

Other signals:


WebView application risks

FedCM does not work in WebView.


Ongoing technical constraints

None

Debuggability

Same as other FedCM features. The network view in devtools would be 
especially helpful for debugging this feature.


Will this feature be supported on all six Blink platforms (Windows, Mac, 
Linux, ChromeOS, Android, and Android WebView)?

No, FedCM in general is not supported on webview. Supported on all other 
blink platforms.


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/fedcm/fedcm-well-known-validation?label=experimental&label=master


Flag name on about://flags

fedcm-well-known-endpoint-validation


Finch feature name

FedCmWellKnownEndpointValidation


Requires code in //chrome?

False


Estimated milestones

Shipping on desktop

145

Shipping on Android

145



Link to entry on the Chrome Platform Status

https://chromestatus.com/feature/4614417052467200


This intent message was generated by Chrome Platform Status 
<https://chromestatus.com/>.

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