Allows FedCM to show multiple identity providers in the same dialog. This provides developers with a convenient way to present all supported identity providers to users. We are planning to first tackle the simple case of having all providers in the same get() call. We are also removing support for ‘add another account’ in FedCM passive mode. This feature allows showing a ‘use another account’ button alongside other IdP accounts in the chooser. The feature is currently unused, and UX conversations have led us to believe that supporting this leads to a more complicated flow without much benefit. This feature will still work in FedCM active mode.
Currently, the FedCM API enables RPs to show federated login prompts to users without requiring the use of third-party cookies. However, the API only supports showing one IDP at a time. Many RPs support more than one IDP, so extending the API to allow showing more than one IDP will benefit these RPs and let users choose an account from the IDP of their choice.
Explainers: https://github.com/fedidcg/FedCM/blob/main/proposals/multi-idp-api.md