What it changes
Registration lock adds a secret beyond control of the phone number when someone attempts to register an account on another device. Signal uses its Signal PIN for this optional protection. A person who intercepts a verification message may still be unable to complete the registration without that PIN. It does not make a stolen, unlocked phone safe and it does not encrypt or back up your chat history.
The tradeoff
If you enable Signal's Registration Lock and forget your PIN, Signal says you may be unable to register again for up to seven days. Signal cannot reset or recover that PIN for you. A new phone migration therefore needs preparation: keep the PIN accessible through a secure method and plan message transfer or backup separately. See Signal's
PIN documentation before changing the setting.
When it is useful
Registration lock helps against number takeover, including some SIM-swap scenarios. It is only one layer. Protect the carrier account, use a phone screen lock, and inspect linked sessions if you suspect unauthorized access. Our
SIM-swap explanation covers the number-control problem separately.
