Field Guide to Bridges

Potential Loss of Assets

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.

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What is a bridge?

A bridge is an app that allows you to transfer assets (cryptocurrencies, NFTs, or other tokens) between one blockchain and another. For example, transferring from BSC to Ethereum.

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 xDai, 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 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.

Network Profiles

For detailed information regarding a specific network, see our Network Profiles, which includes bridge information for each network.

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.

Bridges

Celer Bridge Wormhole's Portal Bridge Rainbow Bridge Terra Bridge
Multichain 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.

I need step-by-step instructions on how to use 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
  • Log in to the app with your MetaMask wallet
  • Choose the network you're going from and to
  • Choose the asset you're bridging from and to
    • During these steps, you may need to sign approvals in your MetaMask Wallet. Make sure you read every transaction or approval you make carefully. For more on approvals, see here.
  • 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.

 

 

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