canonical bridge

A canonical bridge is the official bridge that a rollup or L2 ships as part of its own protocol, as opposed to the many third-party bridges that spring up around it. It is 'canonical' because the L2's designers built and endorse it, and because the wrapped balances it produces are treated as the genuine, native version of an asset on that L2. For a rollup, the canonical bridge is the trust anchor: deposits and withdrawals through it inherit the rollup's full security, since they are settled on the L1 the rollup posts to.

Its security model follows the rollup type. On a ZK rollup, a withdrawal is finalized once a validity proof of the L2 state is verified on L1 — minutes to hours, depending on proving cadence. On an optimistic rollup, withdrawals must wait out the challenge period (typically about seven days) during which a fraud proof could revert an invalid state, which is why bridging out of an optimistic rollup feels slow. In both cases the canonical bridge requires no extra trusted committee beyond the rollup's own settlement guarantees.

That slowness is the gap third-party bridges fill. 'Fast' bridges let you withdraw in minutes by fronting you the funds from a liquidity pool on L1 and taking the slow canonical exit themselves — convenient, but you have now traded the rollup's native security for that bridge's weaker trust assumptions. The general rule: the canonical bridge is the safest path off a rollup, third-party bridges are faster but add risk, and an asset on an L2 is most trustworthy when it arrived through the canonical bridge.