Bridge
A protocol that allows assets to be transferred between different blockchains. Bridges enable users to move collateral from Ethereum to cheaper L2 networks for lending.
Every blockchain is its own island. Ethereum doesn't natively talk to Arbitrum, and Arbitrum doesn't talk to Solana. A bridge is the ferry service — a protocol that locks your asset on one chain and mints an equivalent representation of it on another.
For lenders and borrowers, this matters because the same USDC earning 3% on Ethereum mainnet might earn 7% on a Layer 2 like Base or Arbitrum — and bridging is the only way to get there. The rate differential exists partly because mainnet is expensive and L2 liquidity is still building.
How It Works
Most bridges work through a lock-and-mint mechanism. You deposit 1 ETH into a bridge smart contract on Ethereum. That contract locks your ETH and signals a corresponding contract on the destination chain to mint 1 "wrapped" ETH — a token that represents your original asset.
When you want your original ETH back, you burn the wrapped version on the destination chain. The bridge contract on Ethereum then releases your locked ETH. The round trip typically takes seconds to minutes, depending on the chains involved and how the bridge handles message verification.
Say you hold $10,000 in USDC on Ethereum and want to post it as collateral on an Arbitrum lending protocol. You bridge it, receive $10,000 in USDC.e (Arbitrum's bridged USDC), and deposit that into the protocol. Your collateral is now on Arbitrum — but the underlying dollars are still locked in a contract on Ethereum mainnet.
Why It Matters
Bridges are what make multi-chain yield strategies possible. Without them, your capital is stuck on whichever chain you bought it on. With them, you can chase better rates, lower gas fees, and deeper liquidity pools across a dozen networks — without selling your underlying asset.
What is Smart Contract?
Self-executing code on a blockchain that automatically enforces the terms of an agreement. All DeFi lending protocols operate through smart contracts that handle deposits, loans, interest, and liquidations.
Full glossary entryBill's Take
In 25 years of mortgage lending, moving money between institutions meant wire transfers, correspondent bank relationships, and settlement delays measured in days. Bridges compress that to minutes — but they introduce a new layer of smart contract risk that a wire transfer never had. The speed is real. So is the exposure.
What to Watch
Bridges are consistently the most exploited infrastructure in crypto. The bridge contract holding your locked assets is a single, high-value target. When a bridge is hacked, the wrapped tokens on the destination chain can lose their peg instantly — your "$10,000 in USDC.e" can become worth far less if the backing is gone.
Bridge Risk Is Real
Bridge hacks have resulted in some of the largest losses in crypto history. Before you bridge collateral, check whether the bridge has a current third-party audit, how long it has been live, and whether it has a bug bounty program. A newer bridge with a higher APY on the other side is not worth the counterparty risk on your principal.
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