Crypto glossary
Canonical bridge (native bridge)
A canonical bridge is the official bridge of a rollup or chain, built into its protocol, as opposed to third-party bridges that connect it to other networks.
Every rollup has a canonical bridge: the contracts on Ethereum and on the L2 that are part of the rollup's own design. Deposits lock assets in the L1 contract and mint them on the L2; withdrawals are released on L1 only once the rollup's proof system confirms the state, after the challenge period for optimistic rollups or proof verification for ZK rollups. Sidechains and other L1s also call their official bridge canonical.
For a rollup, the canonical bridge holds most of the assets secured by the chain, and its security equals the rollup's own: if the proofs and upgrade process are sound, so is the bridge. Tokens bridged through it are often considered the reference version, though issuers increasingly prefer native minting, as with USDC replacing bridged USDC.e.
Canonical does not mean safest in every case. On a stage 0 rollup, whoever controls the upgrade keys controls the bridge. Canonical bridges are also slower and support fewer assets than third-party alternatives, so many users never use them, and a token from a third-party bridge may not be redeemable through the canonical one.
Example
A user deposits ETH to Arbitrum through the official bridge and receives it in about ten minutes, knowing that withdrawing the same way will take around a week.