Interoperability is one of the features on which the Polkadot ecosystem is built. Seamless transactions between chains connected to the main relay chain. However, there are other options when transferring tokens to or from external chains, like sending tokens from Ethereum or Kusama to the Polkadot ecosystem.


Keep reading to learn the types of token transfers among different networks and how all of them are secured and powered by Polkadot.


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Cross-chain transfers


Not all transfers between chains are the same. How they interact and the infrastructure shared define the type of protocol a transaction must follow to reach the destination chain. Below, there's a brief differentiation among the different kinds possible in Polkadot:

  • Teleports: They are transfers between a system chain (e.g., Asset Hub, People, etc.) and its relay chain.
  • XCM: Transfers between rollups connected to the same relay chain or between a rollup and the relay chain (e.g., from Bifrost to Hydration, or Moonbeam to the relay chain).
  • Bridges: Transfers between chains that do not share the same validator set must go through bridges. For instance, if you want to send tokens from Ethereum to Polkadot, Polkadot to Kusama, or Arbitrum to Polkadot, you must use bridges.


Even though it's useful to understand the different types of cross-chain transfers, you don't need to decide which one to use every time you make a transfer. Interfaces like Turtle handle that for you.


If you'd like to learn more about bridges, continue to the next section. Or, if you want to explore how Turtle and Hyperbridge simplify the process, skip ahead to the last section.

What are bridges?


But what exactly are bridges, and why are they often viewed with concern? Transfers where the origin chain does not share the same set of validators as the destination chain (cross-consensus transfers) require bridges to connect the two networks. There are different ways to build this communication, but a common distinction is between trusted and trustless bridges.


Trusted bridges are generally controlled by a committee through a multi-signature account. When you use one of these bridges, you are placing trust in the owners of that account. While this setup can be relatively secure, trusted bridges have historically been one of the biggest points of failure in the blockchain industry, leading to loss of funds.


On the other hand, trustless bridges rely entirely on the code they are built on. There are no multi-signature accounts and no need to place trust in any individual or group. They are generally considered more secure than trusted bridges and are the type described in the sections below.

Trustless bridges on Polkadot


⛔ READ THIS FIRST! 


Since bridges might rely on different protocols, the apparently same token on one network may actually be different tokens if they were bridged through different protocols (e.g., "Snowbridge DOT" vs "Hyperbridge DOT").

If you transfer a token using one bridge, do not use a different bridge to return it to the original chain. Otherwise, you risk losing your funds.


Polkadot offers several solutions for transferring assets between Polkadot and external chains. However, three stand out for being innovative, pioneering, and fully trustless:

  • Snowbridge: A trustless bridge connecting Ethereum with Polkadot and Kusama. It uses on-chain features to check transactions (light clients) on Ethereum and the Bridge system chain to connect the networks. Snowbridge enables you to transfer multiple assets to and from Ethereum and Polkadot rollups.
  • Polkadot <> Kusama: It enables the transfer of wrapped KSM to Polkadot and wrapped DOT to Kusama. This is made possible by deploying light clients to their respective Bridge system chains.
  • Hyperbridge: A trustless bridge that connects multiple chains, not limited to Ethereum or Substrate-based networks (e.g., Base <> BNB Smart Chain). It leverages its own Polkadot rollup and ZK-proofs to facilitate asset transfers.

Where to bridge on Polkadot


The technology behind bridges is important because it ensures secure transactions between chains. However, end users need simple interfaces where each operation is clearly displayed and requires minimal input.


To simplify cross-chain transactions, we recommend two platforms that abstract the complex details and simplify the entire process, providing a seamless user experience: Turtle and Hyperbridge.


Turtle


Turtle uses a familiar interface: you simply connect the account(s) you want to use, select the origin chain, and choose the destination chain for the amount of tokens you indicate. You don't need to know whether both chains share the same validator set, whether the transaction uses another protocol instead of a bridge (e.g., XCM), or even what type of bridge is being used. It's really that simple. 



Depending on the origin and destination chains, Turtle may give you the option to receive a different token, effectively swapping one token for another. For example, you can swap USDT from Hydration to DOT on Polkadot Asset Hub.


‼️ IMPORTANT



Turtle uses decentralized pools to process swaps. Depending on the pool, there may be a risk of slippage that affects the final execution price. Always double-check the amount and value of the tokens you want to receive before approving the transaction.


Hyperbridge


Hyperbridge offers a simple interface that shows all the networks it connects to trustlessly through its protocol.


By selecting the "Source" and "Destination" chains, the Hyperbridge app shows which tokens can be transferred and which cannot. Enter the token amount and destination address to check everything is correct before approving the transaction.



Fees for each transfer and the estimated completion time are displayed before you approve the transaction. Make sure to review this information and monitor each step as the transaction is completed.


‼️ IMPORTANT


Hyperbridge allows you to send tokens to any account on any supported network. Always double-check that the address format is correct and that you fully control the destination account on the corresponding network.

We recommend copying the address freshly each time and verifying it before proceeding with the transaction.


And that's it. Even though Polkadot's multi-chain infrastructure and interoperability may seem complex or overwhelming, there are simple tools that abstract this complexity and make cross-chain transactions as easy as possible.