Watcher (OMG Network)

A watcher, in the OMG Network (formerly OmiseGO), was software run by users or service providers to check that the network's Plasma chain was operating honestly. Plasma is a family of scaling solutions in which a separate chain, run by an operator, handles transactions and posts summaries to the Ethereum blockchain, where users' funds are anchored. Because the operator could in theory publish invalid blocks or withhold data, the design depended on someone watching. Watchers downloaded and checked the chain's blocks, compared them with what was posted to Ethereum and, if they found a problem, signalled that users should withdraw, or exit, their funds to Ethereum within a set window. They could also help challenge invalid withdrawals, an idea related to the fraud proof. Later layer 2 designs, such as rollups, reduced the need for this role.