I am testing FedCM since third-party cookie is phasing out.
I've implemented Google OneTap sign-in successfully for years for my website. You can verify it from live website.
I am now testing opt-in FebCM. In my browser, this setting is enabled:
Sites can show sign-in prompts from identity services.
For third-party cookies, this option is selected: Block third-party cookies.
I've added the data attribute accordingly:
<div id="g_id_onload" data-client_id="***.apps.googleusercontent.com"
data-login_uri="https://localhost:50001/account/external-login-google-one-tap?rurl=~%2F"
data-use_fedcm_for_prompt="true">
</div>
When click the prompt sign-in button after page is loaded, I am getting error:
Error:
When fetching the id assertion endpoint, a 403 HTTP response code was received.
localhost/:1 Provider's token is invalid.
client:48 [GSI_LOGGER]: FedCM get() rejects with IdentityCredentialError: Error retrieving a token.