`datr`

Identifies the browser itself, not the account. Meta uses it to spot suspicious logins, and it is set whether or not you have signed in.

Owner: Meta Platforms, Inc.
Matches: The exact name datr
Needed to Work: No. The site works without it.
Confidence: Verified
Source: https://www.facebook.com/privacy/policies/cookies/?annotations[0]=explanation%2F1_common_cookies_and_uses
Last Reviewed: 2026-09-14

Which Sites

Only on facebook.com, messenger.com and their subdomains. The same name on another site is a different cookie, and is not described here.