Bridge

A protocol or service that enables the transfer of digital assets or data between two distinct blockchain networks, such as moving ETH from Ethereum’s mainnet to a Layer 2 scaling solution.

What is a Bridge?

A blockchain bridge is a specialized protocol or application that facilitates interoperability by allowing digital assets, tokens, or data to move seamlessly between two separate blockchain networks with differing architectures, consensus mechanisms, or ecosystems. For instance, a bridge can transfer ETH from Ethereum’s Layer 1 mainnet to a Layer 2 scaling solution like Arbitrum or Optimism, where transaction fees are lower, and then back to the mainnet when needed. Bridges achieve this by locking or burning assets on the source blockchain and minting or releasing equivalent assets on the destination blockchain, often using smart contracts or trusted intermediaries.

Bridges can be custodial (relying on a trusted third party to manage asset transfers) or non-custodial (using decentralized smart contracts for trustless transfers). For example, the Arbitrum Bridge locks ETH on Ethereum and mints a corresponding amount on Arbitrum, with over 1.5 million unique wallets using it as of 2025, transferring billions in value. However, bridges are critical points of vulnerability; high-profile hacks, like the 2022 Wormhole exploit ($325M stolen), highlight risks of flawed smart contract design or centralized control. Despite these risks, bridges are essential for cross-chain DeFi, NFT transfers, and scaling solutions, with popular examples including Polygon’s PoS Bridge, Optimism’s Native Bridge, and multichain protocols like LayerZero, which support interoperability across ecosystems like Ethereum, Solana, and Binance Smart Chain.