Field Guide to Bridges
Transferring assets between networks can be done easily with MetaMask. Just click the 'Swap' button on your homepage to start!
What is a bridge?
A bridge is a method to swap your tokens across different blockchain networks. For example, perhaps you want to use a dapp or a game on the Linea network, but most of your funds are on Ethereum mainnet. You can use a bridge to transfer some ETH, USDC, or other tokens from Ethereum to Linea, and swap them into different tokens if you'd like. You'd then have what you need to start using dapps on Linea.
With MetaMask, this can be done by clicking the 'Swap' button and selecting the network and token you want to exchange.
Why do I need to use a bridge?
- Many users use the same address on multiple blockchains, for example by adding a blockchain connection in MetaMask. What if they've got an NFT on Gnosis Chain, but they want to have it on Polygon?
- Conversely, you might have a different address, say on BSC, than what you use on Ethereum. You may think that you can just send tokens from your BSC address directly to your Ethereum address; after all, they're both EVM-compatible, right?
Wrong. The BSC blockchain and Ethereum blockchains are separate networks, with no built-in knowledge of each other.
If you send to your Ethereum address from BSC, BSC will send to the address you put in, but on the BSC network. For more information on this specific scenario, see here.
What bridge should I use?
You can now access a curated, straightforward bridging experience through MetaMask Swaps. Learn more.
You should choose a bridge primarily based on what you're trying to move, where. For example, some bridges only move ERC-20 (currency) tokens; others specifically handle ERC-721 and 1155 (NFTs). The last thing you want to do is try to transfer tokens to a different network, and never receive them.
There is no definitive listing of bridges.
This is web3, which is based around permissionless, open development; this means that at any given time, there might be a new bridge between networks. There are also bridge aggregators, which are platforms that allow you to use several bridges in conjunction, conveniently transferring assets across platforms.
The following is a non-exhaustive list of bridges and aggregators, in no particular order. MetaMask does not recommend or endorse any of these products; we are providing this information as a starting point for you to do your own research and understand how each bridge works before using it. We recommend using MetaMask's built-in feature, Swaps, for transfers.
Bridges
| Celer Bridge | Wormhole's Portal Bridge | Rainbow Bridge | Terra Bridge |
|---|---|---|---|
| Allbridge | EvoDeFi Bridge | PolyBridge |
Bridge Aggregators
| Rango Exchange | Li.Fi Bridge Aggregator | movr.network |
|---|---|---|
| chainswap | Router Protocol |
How does a bridge work?
There are a number of different mechanisms that bridges use to move assets between networks; often, they are centralized entities that operate almost like an exchange. Others are more decentralized. If you're interested in the nuts and bolts, start with ethereum.org's documentation here.
At their most basic level, bridges are platforms with contracts on the chains you're transferring to and from. Though the exact system varies, each bridge has a mechanism to validate your deposit on one network and issue equivalent tokens on another network.
When you request to move Ethereum from Mainnet to Polygon, for example, the first thing the bridge will need to do is have you deposit the ETH to the bridge. The bridge will prompt you to sign a transaction to send the tokens to their address (for tokens other than ETH, this assumes you've already signed an approval granting it access to your tokens).
The deposit may be validated in a few different ways depending on the bridge, but this process essentially buys you the right to have your target address credited with the agreed amount of tokens (that is: the token you're bridging to). The bridge honors this request by minting or sending the tokens to the account you specified on the destination network.
I need step-by-step instructions on how to use a bridge
Transferring assets between blockchains is not necessarily a simple task. Some tokens cannot be sent from one network to another — and if you do, you can lose them forever. Always do your own research before using a bridge.
Given the above-mentioned wide variety in bridge platforms, networks, and functionality, we can't provide a step-by-step that will work for every bridge. In general, though, this is how it works:
- Navigate to the bridge that you have identified will work for your particular combination of networks and token types
- Connect to the app with your MetaMask wallet
- Choose the network you're going from and to
- Choose the asset you want to transfer
- Initiate the bridging process
- WAIT
- Bridging generally is not instantaneous, and can often take five to ten minutes for the transaction to be fully processed on the first chain, and then the second chain.
- Open your wallet on the second chain (If you're managing both chain's assets in MetaMask, make sure you switch networks in MetaMask!) and verify the assets are present; remember, you may need to add the tokens to be able to see them.