Bridge

A bridge is a protocol designed to move assets or value from one blockchain to another — blockchains that otherwise have no native way to communicate with each other.

Because separate blockchains are, by design, independent systems with no built-in awareness of each other's state, moving an asset "across" chains generally works by locking or burning it on the source chain and minting or releasing an equivalent representation on the destination chain, coordinated by the bridge protocol in between. Some bridges are operated by a small trusted set of parties, and others attempt to be more trust-minimized using cryptographic proofs, but every design still introduces a dependency — on the bridge's contracts, its operators, or both — that doesn't exist when an asset simply stays on its native chain.

That dependency is exactly why bridges matter to understand before using one: they've been, by a wide margin, one of the most frequently and severely exploited categories of infrastructure in crypto, because concentrating value in a bridge's contracts or custody makes it an especially attractive target. This doesn't mean every bridge is risky in the same way, but it does mean the choice of which bridge to use — and how much value to route through it at once — deserves more scrutiny than a typical same-chain swap.

This is directly relevant to swapping crypto across networks: whenever you're moving an asset from one chain to another as part of a swap, a bridge (or a bridge-like mechanism built into the exchange flow) is doing that work behind the scenes. Understanding that a cross-chain step introduces this additional layer of risk, distinct from the swap's own spread or slippage, is worth knowing even if you never interact with a bridge's interface directly. The cross-chain bridge risks guide covers this in more depth, including questions worth asking about any bridge before trusting it with meaningful value.

Bridges are also the standard way to move assets onto and off of Layer 2 networks, and — like any on-chain transaction — bridging involves gas fees on the networks involved, sometimes on both ends of the transfer. Bridged assets used in DeFi, including in liquidity pools, also carry the compounded consideration of impermanent loss on top of whatever bridge risk was involved in getting the asset there in the first place.