The primary authentication method recommended by the Nest Home Assistant integration called Desktop, Installed App or OOB auth was deprecated for new uses on February 28th, 2022 and will be disabled for all users on October 3, 2022. See the Google Developer blog for announcement details.
Existing must upgrade to Web Auth credentials by October 3, 2022.
New users may sign up using Web Auth without issue. Follow the documentation which has been updated to use Web Auth and a My Home Assistant redirect URL using Home Assistant
2022.6 or newer.
If you previously successfully configured Nest and Home Assistant with App Auth then follow the instructions for Deprecated App Auth Credentials.
Nest is now configured entirely from the UI using Application Credentials and the configuration flow will walk you through the steps of creating new credentails the right way.
You will need to upgrade to Web Auth before October to avoid interruption.
Users who signed up using Web Auth are not affected by the App Auth deprecation. However, as of
2022.6 the My Home Assistant URL is now the default redirect URL and may need to be updated in the Google Cloud Console to avoid a
redirect_uri_mismatch (more info).
The OAuth out-of-band flow was designed to support native applications that cannot support a redirect URI like a Web application, which was convenient for Home Assistant since it is difficult for end Home Assistant users to set up SSL certificates and DNS needed for a secure Web endpoint. However, Google has deprecated the OOB flow as it introduces a phishing risk. New users are no longer allowed to create new Desktop auth credentials and existing users will no longer work starting October 3, 2022.
2022.6 the Web Auth OAuth2 flow uses the My Home Assistant redirect URL which handles SSL. This is what allows new signups for Web Auth as the new recommended approach.