The “First seen by this device” date in Messenger’s key verification refers to when your current device first detected that particular encryption key, not when the secret conversation started.
What it means:
- Shows when your device first encountered the other person’s device key
- Usually corresponds to when they logged into that specific device
- Can also appear when they reinstalled Messenger or reset their phone
Key points:
Pros of this indicator:
- Helps verify you’re talking to the same device/person
- Alerts you if a new device suddenly appears
- Useful for detecting unauthorized access
Cons:
- Doesn’t show actual conversation start date
- Can be confusing if they switch devices frequently
- Multiple devices create multiple “first seen” dates
Important: If the date changed recently or you see multiple keys, it could mean they’re using a new device, reinstalled the app, or potentially someone else accessed their account. For relationship concerns, this alone isn’t conclusive proof of anything suspicious—device changes are common.
Check if they recently got a new phone or reinstalled Messenger before jumping to conclusions.