GlossaryAdvanced
Watchtower (Lightning Network)
A third-party service that monitors a Lightning Network channel for fraudulent closure attempts while the channel's owner is offline.
A watchtower is a service that monitors a Lightning Network payment channel on a user's behalf, watching for an attempt by the other party to close the channel using an outdated, more favorable balance — a type of fraud a channel participant could otherwise only catch by being online and watching the chain themselves.
If a watchtower detects such an attempt, it can broadcast a penalty transaction, generally allowing the honest party to claim the dishonest party's channel funds as a deterrent against the attempt in the first place.
Examples
- A Lightning user who can't stay online continuously can rely on a watchtower service to catch a fraudulent channel-closure attempt on their behalf.
- Watchtowers address a specific practical limitation of payment channels: the need for a participant to be able to detect and respond to fraud in a timely way.