As the demand for different blockchain-based Web 3.0 technologies continues to grow, so too does the need to enable interoperability. This is something that is enabled with cross-chain bridge services.
Blockchain is a distributed ledger technology that uses cryptography to provide assurance and integrity to data and transactions. Blockchain networks enable many types of services, including secured databases, immutable ledgers, decentralized applications (dApps), decentralized finance (DeFi), non-fungible tokens (NFTs) and cryptocurrencies.
There are many blockchain networks and cryptocurrencies that use different blockchain technologies, including Bitcoin, Ethereum, Avalanche, Polygon, Solana and Arbitrum. Enabling interoperability and exchange across different blockchain networks is an area where cross-chain bridges -- sometimes also referred to as blockchain bridges -- play an increasingly important role.
What is a cross-chain bridge?
A cross-chain bridge enables an exchange of information, cryptocurrency or NFTs from one blockchain network to another. It enables the flow of data and tokens across what would otherwise be siloed sets of data on different blockchains.
With fiat currency there are many established ways for individuals and businesses to exchange money, creating a globally available and interoperable system of financial payments. Those systems include financial institutions, banks and credit cards that handle foreign exchange. In the world of blockchains, a cross-chain bridge serves an analogous purpose.
Exchange across different blockchains for cryptocurrency is possible without a cross-chain bridge, but it is expensive and more time-consuming. Without the use of a cross-chain bridge, users must first convert a cryptocurrency token into a fiat currency, which often involves fees. They then use currency to get the other desired type of cryptocurrency, incurring more fees and taking time.
One characteristic of a cross-chain bridge is that it enables users to exchange one cryptocurrency for another without first changing it to fiat currency. Cross-chain bridges aren't limited to just cryptocurrency value transfer either. An effective cross-chain bridge can also enable the transfer of smart contracts and NFTs from one blockchain environment to another.
There are several approaches to enabling transfers with a cross-chain bridge. One common approach is using a wrapped token issued by the cross-chain bridge provider platform. With a wrapped token, the value of one token from a specific blockchain network can be encapsulated inside another token. Wrapped tokens are typically based on the ERC-20 technical specification for an Ethereum network. For example, WBTC is a Bitcoin token wrapped with an ERC-20 Ethereum smart contract.
Another approach to enabling cross-chain bridge transfers is by using a liquidity pool. With a liquidity pool, a cross-chain bridge provider holds inventory -- or pools -- of various coins where one can be exchanged for another.
Cross-chain bridges can also be a lucrative target for hackers. One of the largest attacks occurred in February 2022, when cross-chain bridge platform Wormhole was the victim of an attack in which the threat actor stole 120,000 wrapped Ethereum tokens -- worth an estimated $320 million at the time of the theft. BNB Chain, also known as Binance Smart Chain, was the victim of an attack in October 2022 that resulted in losses estimated at $570 million. Blockchain bridge analysis vendor Chainalyis has estimated that 69% of cryptocurrency funds stolen in 2022 have been attributed to attacks on cross-chain bridges.
Learn more about how cryptocurrency cyber attacks are on the rise.
Best cross-chain bridges
For Bitcoin, which is perhaps the most well-known cryptocurrency, the most common bridge is with the use of Wrapped Bitcoin (WBTC). Wrapped Bitcoin is sometimes referred to as a blockchain bridge, as it enables Bitcoin as an ERC-20 token -- a token specification that is supported on many other blockchains.
While Bitcoin is well known, the Bitcoin blockchain doesn't have the same smart contract features that are the foundation of Ethereum-based blockchains. Smart contracts enable decentralized finance, decentralized apps and NFTs. Users looking to use Bitcoin across other blockchain networks will first need to covert to Wrapped Bitcoin. This was originally run as a blockchain bridge by BitGo, and in 2022 is supported and available via a growing partner network of exchanges.
Cross-chain bridge providers often support multiple types of blockchains, though specific support varies from provider to provider. Support for bringing smart contracts, tokens and NFTs from the Ethereum mainline to different blockchain networks is among the most common feature across cross-chain bridges.
When choosing a cross-chain bridge, users should be sure the specific blockchain network -- as well as token or NFT -- they are looking to bridge is supported. Different networks also have varying fees, which can be volatile and change quickly.
Here are some popular cross-chain bridges:
The Celer cBridge uses the Celer State Guardian Network to enable liquidity across different blockchains.
Supported blockchain networks: Ethereum, Astar Network, BNB Chain, Avalanche, Polygon, Arbitrum, Fantom, Metis Mainnet, Oasis Emerald, Celo, Aurora, Harmony, Moonbeam, Moonriver, Optimism, Boba Network, OKExChain, Heco, Clover, Gnosis Chain, Milkomeda Cardano and Shiden.
Supported cryptocurrency tokens: Tether, USD Coin, Ethereum, MetisDAO, Kromatika, Binance USD, Thales, Domi Coin, Dodo, Unified Society, Lyra, JPEGvault, Immutable X, dForce, xToken, Wootrade, Perpetual Protocol, Mask Network, Izumi Finance, MCDex, PolkaEx, CEC Energy Chain, PerlinX, Reef Chain, Boba Network and Standard Protocol.
This platform was developed by the Germany-based Tixl organization, which rebranded as the Autobahn Network in March 2022. Cross-Chain Bridge has support for bridging both tokens and NFTs across multiple networks.
Supported blockchain networks: Avalanche, BNB Chain, Polygon, Ethereum and Fantom.
Supported cryptocurrency tokens: Bridge, Bulk Token, Candle, DAEX Token, GamyFi Platform, TribeOne, Moonie NFT, Polychain Monsters, Realm Token, Autobahn Network, UnitedCrowd Token, Unobtanium, Upfire, USD Coin, Tether and Wrapped Ethereum.
Formerly known as Fantom Anyswap, Multichain positions itself as a cross-chain router protocol, enabling the flow of data and assets across different blockchain networks. No other cross-chain bridge service supports as many token types as Multichain.
Supported blockchain networks: Arbitrum, Astar Network, Aurora, Avalanche, Bitcoin, Blocknet, BNB Chain, Boba Network, Celo, Clover, ColossusXT, Conflux eSpace, Cronos, Ethereum, Fantom, Fuse, Fusion, Gnosis, Harmony, Huobi, IoTex, KCC, Litecoin, Metis, Milkomeda, Moonbeam, Nebulas, OEC, Oasis Network, Optimism, Polygon, REI, Shiden Network, Syscoin NEVM, Telos, Terra, Velas and XRP.
Supported cryptocurrency tokens: View the full list of tokens here.
Portal Token Bridge (formerly known as Wormhole)
The Portal Token Bridge is powered by the Wormhole protocol that enables transfers of both tokens and NFTs across different chains.
Supported blockchain networks: Acala, Algorand, Aptos, Arbitrum, Aurora, Avalanche, Binance Smart Chain, Celo, Ethereum, Fantom, Injective, Karura, Klaytn, Moonbeam, Near, Oasis, Polygon, Terra and Terra Classic.
Supported cryptocurrency tokens: USD Coin, Tether, FTX Token, Ethereum, Serum, MakerDAO, TerraUSD, Binance USD, Huobi Global, OKEx, Frax Protocol Token, Huobi BTC, Synthetix, Shiba Inu, Axie Infinity, SushiSwap, Decentraland, The Sandbox and Uniswap.
The Synapse protocol enables secure cross-chain communication through its universal interoperability model.
Supported blockchain networks: Ethereum, Arbitrum, Avalanche, BNB Chain, Optimism, Polygon, Aurora, Boba Network, Canto, Cronos, DFK Chain, Fantom, Harmony, Klaytn, Metis, Moonbeam, Moonriver.
Supported cryptocurrency tokens: USD Coin, USD Tether, DAI, Ethereum, Synapse, Wrapped Bitcoin, ChainLink Token, Angle Euro, Frax, Olympus DAO, Highstreet, New Order and Vesta.
Umbria Narni Bridge
The Umbria Narni Bridge enables blockchain asset transfer using liquidity pools, where assets are held across multiple chains.
Supported blockchain networks: Polygon Mainnet, Ethereum Mainnet, BNB Chain, Avalanche. Plans to support Fantom, Ronin, Solana, Cardano, Immutable X, Worldwide Asset Exchange, Gnosis, KuCoin Community Chain and Huobi Eco Chain.
Supported cryptocurrency tokens: Ethereum, Polygon, Tether USD, Umbria Governance Token, USD Coin and Wrapped Bitcoin.