This skill should be used when implementing CCTP (Cross-Chain Transfer Protocol) for USDC bridging, working with Circle's attestation API, understanding CCTP domains and finality, or building crosschain transfer features. Use for "burn and mint", "CCTP transfer", "attestation", "crosschain USDC", "Bridge Kit", "fast transfer", "TokenMessenger", "MessageTransmitter", or "Iris API" tasks.
This skill should be used when implementing CCTP (Cross-Chain Transfer Protocol) for USDC bridging, working with Circle's attestation API, understanding CCTP domains and finality, or building crosschain transfer features. Use for "burn and mint", "CCTP transfer", "attestation", "crosschain USDC", "Bridge Kit", "fast transfer", "TokenMessenger", "MessageTransmitter", or "Iris API" tasks.
CCTP is a permissionless onchain utility that securely transfers USDC between supported blockchains by burning tokens on the source chain and minting them on the destination chain. Circle created CCTP to improve capital efficiency and reduce trust assumptions compared to traditional lock-and-mint bridges.
When to Use This Skill
Use this skill when:
Implementing USDC crosschain transfers with burn-and-mint
Working with Circle's Attestation Service (Iris API)
Understanding CCTP domains and chain mappings
Choosing between Fast Transfer and Standard Transfer
Calculating fees for crosschain transfers
Implementing hooks for post-transfer automation
Debugging attestation or finality issues
Integrating with Bridge Kit SDK
Transfer Methods
Fast Transfer
Fast Transfer enables faster-than-finality transfers using Circle's Fast Transfer Allowance:
User burns USDC on source chain
Attestation Service attests after soft finality (~8-20 seconds)
Fast Transfer Allowance backs the transfer until hard finality
USDC mints on destination chain with fee deduction
Allowance replenishes after source chain finalizes
Best for: Speed-sensitive use cases, typical transfers under 30 seconds.
Standard Transfer
Standard Transfer waits for hard finality before attestation:
User burns USDC on source chain
Attestation Service waits for hard finality (13 minutes to 32 hours)
Attestation issued after full confirmation
USDC mints on destination chain
Best for: Large transfers, when finality guarantees are critical.
Critical Concepts
CCTP Domains
Domains are Circle-issued identifiers for blockchains. They do not map to public chain IDs.
