Configuring Sign-In using Google
Enabling the Google Sign-In Integrations enables visitors and customers to register, sign in, and connect their Google accounts with your WHMCS installation for faster signup and automatic sign-in.
Configuring Sign-In with Google
Watch the video tutorial for this feature. 
Google Sign-In Integration requires a Google Developer Project and API credentials. You can create this using your existing Google account. Users will only see the app name you define and will not see anything relating to the account you use to create the project.
To do this:
- Visit https://console.developers.google.com/.
- Log in to your Google account. Changing the Google account you use to create the app requires users to re-authenticate and re-link their accounts.
- Choose Create project.
- Enter a project name and click Create.
- On the project dashboard, select Credentials in the left sidebar.
- For the OAuth consent screen configuration, enter a product name, homepage URL, and logo URL.
- Click Save.
- Go back to the Credentials tab and select Create credentials > OAuth client ID.
- Choose Web application.
- Enter your full root domain in both the authorized JavaScript origin and redirect URI boxes.
- Click Create.
- Save your client ID and secret, which you will use to activate Google Sign-In within WHMCS.
- Log in to the WHMCS Admin Area.
- Navigate to Configuration () > System Settings > Sign-In Integrations or, prior to WHMCS 8.0, Setup > Sign-In Integrations.
- Select Activate under the Google heading.
- Enter your Google client ID and secret.
- Click Save & Activate.
WHMCS will attempt to validate the details you have entered. If the client ID and secret are valid and successfully authenticate with the Google API, the values will be saved.
For troubleshooting help, please refer to Troubleshooting Sign-In using Google