How does a crypto bridge move tokens between chains?
Blockchains can't talk to each other on their own, so bridges link them.1 Many bridges don't really move your tokens: they lock or burn them on one chain and mint matching tokens on the other.2,3
Why bridges exist
Each blockchain is built on its own, with its own rules. So chains cannot talk to each other natively, and tokens cannot move freely between them.1 Bridges connect blockchains, so that information and tokens can pass between them.1
A common reason to use one is to move ETH from Ethereum to a layer 2 rollup, to pay lower fees.1 You can also move funds back to Ethereum later.4
Three ways to move value
Many bridges don't physically carry tokens from one chain to another. Instead, they usually mint and burn them.3 ethereum.org says three ways to move value between chains stand out:2
- Lock and mint. Lock the tokens on the first chain, and mint the same amount on the second chain.2
- Burn and mint. Burn (destroy) the tokens on the first chain, and mint new ones on the second chain.2
- Atomic swap. Swap your tokens on one chain for another person's tokens on the other chain.2
A token minted to stand for an asset on another chain is often called a wrapped token.5 For example, WBTC is a token on Ethereum that stands for bitcoin. It is not the original bitcoin on the Bitcoin blockchain.1
A rollup's own bridge
To use a rollup, you deposit tokens into its bridge contract on Ethereum. The same amount is then minted to your address on the rollup.6 To leave, your tokens on the rollup are burned, and you claim the locked funds back on Ethereum.6,7
A bridge built by a network to help people move funds onto it is called a native bridge. The Arbitrum Bridge is one example.2
We name networks and bridges only as examples of each type. Naming one is not a recommendation.
Trusted and trustless bridges
Trusted bridges depend on a central company or group to run them. Users rely mostly on the operator's reputation.1 They use an outside group of verifiers, such as a set of signers who must approve each transfer.2
Trustless bridges rely on the chains they connect, and add no new parties to trust.2 ethereum.org says they are considered more secure than trusted bridges.2 Many bridges sit somewhere between the two.1
| Trusted bridge | Trustless bridge | |
|---|---|---|
| Who checks transfers | An outside group of verifiers2 | The connected chains and their validators2 |
| What you rely on | Mostly the operator's reputation1 | The security of the chains themselves1 |
| Typical strengths | Speed, low cost, many chains2 | Security2 |
Why bridges are targets
Bridges often keep one central store of funds that backs all the bridged tokens. That store becomes a target.8 The chief scientist at Elliptic, a blockchain analysis firm, told CNN that bridges are "huge honeypots".5
The risks
- Smart contract risk: a bug in the code can cause users to lose funds.1
- Censorship risk: the operators of a trusted bridge could, in theory, stop you moving your tokens.1
- Custodial risk: the operators of a trusted bridge could work together to steal users' funds.1
- Knock-on risk: many bridges use wrapped tokens, and wrapped tokens have been exploited, which puts the wider system at risk.2
- Introduction to blockchain bridges. ethereum.org, updated 24 July 2026.
- Bridges. ethereum.org developer docs, updated 3 April 2026.
- Sidechains. ethereum.org developer docs, updated 23 February 2026.
- How to bridge tokens to layer 2. ethereum.org, updated 6 June 2026.
- Another crypto bridge attack: Nomad loses $190 million in 'chaotic' hack. CNN Business, 3 August 2022.
- Optimistic rollups. ethereum.org developer docs, updated 23 June 2026.
- Zero-knowledge rollups. ethereum.org developer docs, checked 22 October 2026.
- Vulnerabilities in cross-chain bridge protocols emerge as top security risk. Chainalysis, 2 August 2022.
General education built from the publicly available sources listed above. Not financial, legal, tax or investment advice. Naming a company, project or regulator is not an endorsement either way. Last checked 2026-10-22. Terms and disclaimer.