Google Classroom add-ons must use Google single sign-on (SSO) to identify and authenticate users.
See Google Identity's OpenID Connect Guide for more information on SSO. We also recommend referencing Google's official documentation on user sign-up and sign-in for automatic sign in and Sign-In Branding Guidelines.
See the frictionless sign-in page for implementation guidance for Google SSO in Classroom add-ons. The frictionless sign-in guide also refers to the test plan that can be used to ensure your add-on is following sign-in best practices.
Sign in flow
To reduce sign-in friction for users, Google Classroom provides two query
parameters when an iframe is opened: login_hint and hd. hd is the user's
domain, and is provided when the user first opens your add-on. login_hint is
the user's unique Google ID, and is provided after the user has signed into
your add-on for the first time. This parameter provides context on the user
that's signed into Google Classroom. See our sign-in parameters guide page
for a more detailed discussion of these query parameters.
When a sign-in dialog is displayed, use the hd query parameter to filter out
invalid domains simplifying the account choices. You must display a Google
sign-in dialog if the login_hint query parameter of the current
Google Classroom user doesn't match any signed-in user of the add-on. The
button must adhere to Google's branding
guidelines. If the user is already signed in, they
shouldn't be prompted to sign-in again.
Figure 1. Sign in flow when a user initially launches
your add-on.
Individual installations add the add-on to the user's own account. Users are prompted to consent to the add-on's access scopes when the add-on is installed individually.
Administrator installations add the add-on to any or all accounts in the domain, and can only be performed by a domain administrator. The administrator can optionally consent to all access scopes on behalf of all users in the domain; users are not prompted to consent to any access scopes if the administrator chooses to do so.
See Installation settings for more information.