What it means
Signal's safety number is unique to a one-to-one chat and helps users detect a change in the encrypted connection. If two people compare it while already knowing each other's identity, a match strengthens confidence in the channel. Merely seeing a number in a chat does not establish that a stranger owns the claimed name.
A real-world example
An impostor starts a conversation using a friend's photo. The chat has a valid safety number, but only a separate call to the real friend reveals the impersonation.
What to do
Compare the number with the person in person or through a previously trusted channel before marking it verified for sensitive use.
The distinction that matters
A number can legitimately change after a new phone or reinstall. A marked-verified number requires new approval before sensitive messaging after a change. The indicator is local to your verification decision; it is not an endorsement from Signal that the human identity was checked.
Signal's safety-number scope
