Is It Safe to Connect Gmail to a Third-Party App?

What you are actually agreeing to

1. 1The consent screen decides everything. Google grants access by OAuth scope, and the scope name — not the app's marketing — is what determines what it can do. Two apps that both say "we help with email" can hold wildly different power.
2. 2The scope to be wary of is https://mail.google.com/. That is full mailbox access, including permanently deleting messages while bypassing Trash. If an app asks for it and cannot explain why, that is your answer.
3. 3A step below is gmail.modify: read every message, read attachments, add and remove labels, create and delete drafts, and send mail. It cannot permanently delete a message — deletions can only go to Trash, where you can recover them.
4. 4Read-only (gmail.readonly) apps cannot label, draft, or send. Anything that files your mail or writes a reply needs write access; an app claiming to do that on read-only scope is describing something else.
5. 5The access outlives the browser session. A refresh token keeps working after you close the tab, log out, or change devices. It stops when you revoke it, or when Google expires it.
6. 6Google requires apps using restricted Gmail scopes to pass verification and an annual third-party security assessment (CASA). It is a real bar, but it is a floor, not a guarantee about any specific app's judgement.

What that actually means

• •The consent screen shows plain-English summaries, not scope names, so "read, compose, send and permanently delete" and "read, compose and send" look nearly identical
• •There is no way to grant Gmail access for a date range or a single label — scope applies to the whole mailbox
• •Granting access to one app does not tell you what it stores, where, or for how long
• •Removing an app from your Google account does not delete data it has already copied