FAQ

Cross-Chain Transfer Protocol (CCTP) is a permissionless onchain utility that facilitates USDC transfers between blockchains via native burning and minting. With CCTP, USDC is effectively teleported from one blockchain to another.

Lock-and-mint bridges are applications that lock a user's native USDC within a smart contract on a source chain and then mint a synthetic or bridged form of USDC on a destination chain. This process incurs additional trust assumptions and can result in poor UX due to the fragmentation of liquidity. In contrast, CCTP enables USDC to move securely 1:1 between blockchains via a native burn-and-mint process. The result is greater capital efficiency and unified liquidity with no creation of bridged forms of USDC. As a low-level primitive, CCTP can be embedded within existing bridge apps to replace their lock-and-mint functionality.

Liquidity pool bridges are applications that hold large pools of USDC on a source chain and a destination chain in order to facilitate cross-chain swaps for end users. This process incurs additional trust assumptions and fees associated with the liquidity tied up on each chain. In contrast, CCTP enables USDC to move securely 1:1 between blockchains via a native burn-and-mint process. The result is greater capital efficiency and unified liquidity without the need for large pools of USDC tokens. As a low-level primitive, CCTP can be embedded within existing bridge apps to replace their liquidity pool functionality. Alternatively, CCTP could be used by the bridge provider to programmatically rebalance their liquidity pools behind the scenes and reduce operational costs.

CCTP serves as a permissionless infrastructure for developers to build on top of, or integrate into, their existing apps, bridges, exchanges, and wallets.

CCTP V1 is intended for developers looking to integrate standard cross-chain functionalities while CCTP V2 is intended for developers looking to integrate advanced cross-chain functionalities for faster speeds and enhanced composability. Learn more about the two distinct versions here.

No, CCTP is permissionless, which means any developer can integrate via Circle's docs and GitHub repository.

For both CCTP V1 and CCTP V2, there is a gas fee charged on the source blockchain and on the destination blockchain. The app that integrates with CCTP is responsible for determining how gas fees are handled.

For CCTP V2 Fast Transfer, an additional fee is collected when the stablecoin is minted on the destination chain, based on the amount minted. Refer to the product fee schedule for more CCTP V2 Fast Transfer fee information.

Circle's Fast Transfer Allowance uses offchain funds to overcollateralize supported stablecoins, enabling message attestation before finalization. This mechanism is only used for CCTP V2 fast transfers, and ensures that the stablecoin remains fully reserved in the event of a mint for which the associated source chain burn is affected by a reorg.

CCTP V1 and V2 are available across multiple blockchains, with more to be announced in 2025. For the latest list, refer to the CCTP supported blockchains page.

Yes, both can co-exist on the same blockchain. For example, CCTP V1 and CCTP V2 are available on Arbitrum, Avalanche, Base, and Ethereum.

Yes, Circle Mint is capable of moving USDC natively across chains. However, Circle Mint is a commercial product that is only available to qualified businesses approved by Circle.

Centralized exchanges typically hold various native forms of USDC liquidity on their platforms. Users with an account at a centralized exchange can deposit USDC (native to a given chain) into their exchange wallet, and then withdraw USDC (native to a different chain) to their external wallet.

In contrast, CCTP is permissionless. This means it's accessible to any developer to seamlessly integrate into their apps and does not require onboarding to Circle. End users can move USDC through a CCTP-enabled app to any supported blockchain at any time. Developers can also compose new onchain experiences on top of CCTP within their apps.

When USDC is burned on the source chain, the event is automatically observed by Circle's Attestation Service. The app facilitating the burn of USDC is responsible for fetching the signed attestation from Circle, which then enables CCTP to mint USDC on the destination chain.

Yes. The CCTP smart contracts have been independently audited by third-party security firms:

• CCTP V1 was audited by ChainSecurity (PDF) and Halborn (PDF).
• CCTP V2 was audited by ChainSecurity (PDF) and OtterSec (PDF).

Refer to the linked reports for detailed findings and audit results.

While its unavailability would temporarily preclude new burn messages from being signed, we anticipate robust uptime and availability similar to how our existing minting services operate today.

CCTP has no direct impact upon existing bridged forms of USDC.

Circle's plans to bring USDC natively to more blockchain networks remain the same and will continue to grow. We envision CCTP establishing USDC as a universal liquidity layer for the Internet that is accessible to all.

WHAT'S NEXT

• CCTP Overview