[null,null,["最后更新时间 (UTC)：2025-08-29。"],[],[],null,["# Sign in\n\nGoogle Classroom add-ons **must** use Google single sign-on (SSO) to identify\nand authenticate users.\n\nSee [Google Identity's OpenID Connect Guide](https://developers.google.com/identity/protocols/oauth2/openid-connect) for more information on SSO. We\nalso recommend referencing Google's official documentation on user sign-up and\nsign-in for [automatic sign in](https://developers.google.com/identity/gsi/web) and [Sign-In Branding Guidelines](https://developers.google.com/identity/branding-guidelines).\n\nSee the [frictionless sign-in page](/workspace/classroom/add-ons/developer-guides/frictionless-signin) for implementation guidance for Google SSO\nin Classroom add-ons. The frictionless sign-in guide also refers\nto the [test plan](/static/workspace/classroom/assets/classroom_add_ons_test_plan.pdf) that can be used to ensure your add-on is\nfollowing sign-in best practices.\n\nSign in flow\n------------\n\nTo reduce sign-in friction for users, Google Classroom provides the\n`login_hint` query parameter when an iframe is opened. `login_hint` is a user's\nunique Google ID, and is provided *after* the user has signed into your add-on\nfor the first time. This parameter provides context on the user that's signed\ninto Google Classroom. See our [sign-in parameters guide page](/workspace/classroom/add-ons/developer-guides/iframes#sign-in_related_parameters) for a more\ndetailed discussion of these query parameters.\n\nYou must display a Google sign-in dialog if the `login_hint` query parameter of\nthe current Google Classroom user doesn't match any signed-in user of the\nadd-on. The button must adhere to [Google's branding guidelines](https://developers.google.com/identity/branding-guidelines). If the user is\nalready signed in, they shouldn't be prompted to sign-in again.\n\n**Figure 1.** Sign in flow when a user initially launches\nyour add-on.\n| **Important:** The sign in button should only be seen when the add-on doesn't have a signed in user to compare against the `login_hint` query parameter. The sign in button is unnecessary if the add-on matches the signed in user using the value of `login_hint`; in this case, the add-on should keep the user signed in."]]
图 1. 用户首次启动插件时的登录流程。