You may have given various websites and services access to some of your gmail data in order for them to perform better. You may no longer be able to utilize certain services as time goes on. It can access your Gmail account even if you don't use it. Periodically review who has access to your account and use the built-in Gmail security features to revoke any permissions that are no longer needed.

The online browser, not the app, is where you'll find Gmail management. To carry out these steps, you'll need a desktop-class browser.

To see which websites and apps have previously been given access to your Gmail account data, go to: Find Apps That Can Access Your Gmail Account

Go to the Google Account control panel's Permissions page.

Google Account permissions
Security settings for Google Account
In the Third-party apps with account access area, have a look at the apps. To see more details about an app's access to Gmail, click on it. Remove Access to revoke permissions.

The Remove Access option has been marked in a Google Account.
Carry on with the other two portions of the screen in the same manner:

Signing in with Google displays the apps that accept Google credentials as an authentication method. Your name, profile photo, and email address are the only things those services can view about you. Your account will not be accessed by these apps.
Google apps displays a list of Google apps that have access to your Google account data.
It's possible that you don't want to disable access to certain websites or apps. If your Gmail syncs with another email provider service or app that you've set up and use, you generally don't want to deny that provider access to your Gmail. Remove access if you are no longer using that email service or app.

The View From Google Apps
A area for Google apps is in the third section of the permitted services page. Although these are all reputable apps now or in the past, you should deactivate access if you no longer use them, as they are likely to have full access to your Google account. If you use the Google Chrome browser, for example, it has complete control over your account. The program has full access to your contacts' names, as well as your private Gmail correspondence and attachments.
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