Intent to Ship: FedCM—Support Structured JSON Responses from IdPs
Chromestatus
Contact emails
sures...@microsoft.comExplainer
https://github.com/w3c-fedid/idp-registration/issues/13#issuecomment-3254858070Specification
https://github.com/w3c-fedid/FedCM/pull/771Summary
Allows Identity Providers (IdPs) to return structured JSON objects instead of plain strings to Relying Parties (RPs) via the id_assertion_endpoint. This change simplifies integration for developers by eliminating the need to manually serialize and parse JSON strings. It enables more dynamic and flexible authentication flows, allowing RPs to interpret complex responses directly and support varied protocols like OAuth2, OIDC, or IndieAuth without out-of-band agreements.
Blink component
Blink>Identity>FedCMWeb Feature ID
fedcmTAG review
https://github.com/w3ctag/design-reviews/issues/1147TAG review status
Issues openRisks
Interoperability and Compatibility
None
Gecko : No signal comments from Ben Vandersloot in https://github.com/w3c-fedid/meetings/blob/main/2025/2025-07-29-FedCM-notes.md#status-of-cr-blockers , No strong opinions
WebKit : No signal
Web developers : Positive
Other signals : This was requested by Identity providers.
Ergonomics
n/a
Activation
n/a
Security
n/a
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?
n/a, FedCM not supported in WebView
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)?
NoFedCM in general is not supported on webview. Supported on all other blink platforms.
Is this feature fully tested by web-platform-tests ?
Yeshttps://wpt.fyi/results/fedcm/fedcm-flexible-token?label=experimental&label=master
Flag name on about://flags
NoneFinch feature name
FedCmNonStringTokenRollout plan
Will ship enabled for all usersRequires code in //chrome?
FalseTracking bug
https://issues.chromium.org/346567168Estimated milestones
| Shipping on desktop | 143 |
| Shipping on Android | 143 |
|---|
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).
noneLink to entry on the Chrome Platform Status
https://chromestatus.com/feature/5153509557272576?gate=5128781719273472
Yoav Weiss (@Shopify)
This seems like a small yet useful addition.
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Alex Russell
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