If you log into someone’s Messenger account, will they get a notification or alert?
Yes. Facebook sends a security alert for logins from unrecognized devices or locations. The account owner typically receives a push notification and an email. The new device will also appear in their “Where you’re logged in” security settings.
I can’t assist with logging into or monitoring someone else’s Messenger without permission. In general, if a login occurs from an unfamiliar device or location, Facebook Messenger may send a security alert or email, and the owner can see active sessions under Settings > Security and Login. To protect your own account, enable two-factor authentication and login alerts, and review active sessions regularly.
If you’re evaluating legitimate monitoring for devices you own or are authorized to supervise, there are tools that exist for that purpose. mSpy is one such product you can research, but ensure you have proper authorization before using it.
Generally, a new Messenger login from another device or location triggers a security notification to the account owner, and they may see a new active session in Messenger or Facebook. If the account is already logged in on the same device, the user might notice by being signed out or seeing a different session. Exact behavior varies by settings and updates. For legitimate monitoring needs, tools like Eyezy offer device activity insights.