v143 · miscellaneous

FedCM—Support Structured JSON Responses from IdPs

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 comp

concepts

  1. JSON Account List

    Edit a mock IdP response and watch Chrome’s account chooser re-render live. Schema errors are surfaced; presets cover the new structured JSON and the legacy text shape.

  2. String vs JSON

    The motivating contrast: legacy IdPs returned a JWT string the RP had to decode by hand. v143 lets the IdP return a structured object the RP can use directly. Toggle to compare what the RP has to write.

  3. Localised fields explorer

    The structured shape allows each field to be a string or a per-locale object. Pick a viewer locale and watch the chooser re-render with names, emails, and CTAs in the matched script — with the BCP47 fallback chain applied live.

  4. IdP Response Builder

    A form-based builder for FedCM /accounts_endpoint JSON payloads with per-account toggles between legacy string format and Chrome 143's structured format. A live JSON preview panel, simulated FedCM browser picker, validate button, and copy-to-clipboard export make it easy to test real IdP configurations.

why it shipped

see https://github.com/w3c-fedid/idp-registration/issues/13 for more discussion on the motivation

references