A blockchain bridge enables the transfer of digital assets, data, or functionality between two independent networks. Because blockchains operate in isolation, bridges solve a fundamental interoperability problem.
A bridge does not physically convert assets but mirrors them on the target blockchain, typically through locking and minting or through custody and issuance (wrapping). This allows users to deploy assets such as Bitcoin within the Ethereum ecosystem without leaving the originating blockchain. Bridges create interoperability and allow users to move assets such as tokens or NFTs across ecosystems.
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Technical functioning
Bridges fundamentally operate using two models: custodial and non-custodial.
- Custodial bridges operate in a centralized manner. A service provider holds the original asset on the source chain and issues a representative token on the target chain (e.g., Wrapped BTC).
- Non-custodial bridges rely on smart contracts and frequently group-based validation (multi-sig, MPC consensus, light-client proofs). In this model, assets are automatically locked and corresponding representations are generated without a central intermediary.
From a user perspective, the process is similar: Token A is “locked” on Chain X, while a 1:1 representation appears on Chain Y. For the return transfer, the representation is burned and the original asset is unlocked. Important: in most cases, the token does not move; it is represented or mirrored.
Use cases and benefits
Bridges enable the movement of liquidity between ecosystems without selling assets. DeFi applications can shift capital from one chain to another to capture yield opportunities. NFTs are also bridged, for example, for marketplaces or gaming ecosystems. Developers benefit by combining functionalities from different chains – such as Ethereum smart contracts with the speed and low fees of alternative networks.
Technically, bridges are among the most complex infrastructures in Web3 and have historically been the largest source of hacks. Failures can occur
- in smart contract implementations
- in multi-signature administration
- in off-chain validator networks
- through flawed pricing or proof systems
Because bridges aggregate significant asset volumes, they are prime attack targets. A compromise often results not only in the loss of the representative token but also in the locked original assets.
