Google Civic Information API

In the Google Cloud Console Credentials page, create or select a project, enable the Civic Information API for that project if needed, then click Create credentials → API key. Restrict the key before production use. Send it as the key query parameter on Civic Information API requests.

In the Google Cloud Console Credentials page, click Create credentials and create the appropriate OAuth 2.0 client for your app type. Use Google's OAuth 2.0 flow described in the Google OAuth 2.0 docs to obtain an access token. The Civic Information docs note OAuth 2.0 is generally for private user data requests and that this API does not have methods requiring OAuth 2.0 authorization, but the discovery document says requests may use an OAuth token instead of an API key.