Definition
An optimistic bridge is a cross-chain messaging and asset-transfer concept that assumes messages between blockchains are valid by default and only reverts them if a fraud condition is proven within a specified challenge window. It relies on off-chain or on-chain actors to monitor state, submit fraud proofs when necessary, and align incentives so that incorrect cross-chain claims can be economically penalized.
In Simple Terms
An optimistic bridge is a way for different blockchains to pass messages or assets by trusting them first and checking them later. Transfers are treated as correct unless someone proves they are wrong within a time limit, at which point the incorrect transfer can be canceled and the dishonest party penalized.
Context and Usage
The term optimistic bridge is commonly used in discussions of cross-chain interoperability, especially where systems mirror the security assumptions of optimistic rollups. It appears in protocol designs that separate data availability from verification and in architectures that use fraud proofs to secure state transitions across chains. It is often contrasted with other bridge concepts that rely on immediate verification or different trust models.