Cross-chain bridge
Also called: crypto bridge · blockchain bridge · bridge
Definition
A cross-chain bridge is a protocol that moves tokens or messages between two blockchains, usually by locking or burning assets on one chain and releasing or minting matching assets on the other.
This entry is shown in English.
How Cross-chain bridge works
Blockchains cannot read each other directly. A bridge connects them. In a lock-and-mint design, you lock tokens in a contract on chain A, and the bridge mints a wrapped version on chain B. Other designs use liquidity pools on both sides, or burn the token on one chain and mint it natively on the other, as Circle's CCTP does for USDC.
Bridges hold large amounts of locked assets, and they rely on validators, multisigs or other mechanisms to confirm what happened on the other chain. That makes them a frequent target: several of the largest crypto hacks were bridge exploits.
Before bridging, check that the bridge is the official or widely used one for that route, that the token you will receive is the version accepted on the destination chain, and what fees and wait times apply. Moving funds through a centralized exchange is sometimes simpler and cheaper.
Example
Suppose you want to move 2,000 USDC from Ethereum to Arbitrum. A bridge quotes a fee of 3 USDC plus Ethereum gas of a few dollars and an arrival time of about 15 minutes. You approve the bridge contract, send the transfer and receive 1,997 USDC on Arbitrum. Alternatively, you could deposit to an exchange on Ethereum and withdraw on Arbitrum if the exchange supports both networks.
Common mistakes
- Using a bridge link from a social media reply instead of the official site.
- Receiving a wrapped token version on the destination chain that local apps do not accept.
- Bridging a large amount without first sending a small test.
Learn and practise
FAQ
Are cross-chain bridges safe?
They carry extra risk because they hold large locked balances and depend on their security design. Many users limit the amount they keep in bridged tokens.
How long does bridging take?
From a minute to several days, depending on the bridge design and the chains. Some official rollup bridges take about a week to withdraw back to Ethereum.