Required Block Confirmations

Block confirmation requirements for attestations on each chain

Before signing an attestation for a source chain event, Circle waits for a specified number of on-chain block confirmations to pass to determine finality. The following table displays the average time it takes for an attestation to become available after a source chain event, which includes the ~20 seconds it takes for the attestation service to observe and sign the source chain event.

Note: These values are subject to change.


Source ChainNumber of BlocksAverage Time
Ethereum~65*~13 minutes
Avalanche1~20 seconds
OP Mainnet~65 ETH blocks*~13 minutes
Arbitrum~65 ETH blocks*~13 minutes
Noble1~20 seconds
Base~65 ETH blocks*~13 minutes
Polygon PoS~200*~8 minutes
Solana32~25 seconds


Source ChainNumber of BlocksAverage Time
Ethereum Sepolia5~1 minute
Avalanche Fuji1~20 seconds
OP Sepolia5~20 seconds
Arbitrum Sepolia5~20 seconds
Noble Testnet1~20 seconds
Base Sepolia5~20 seconds
Polygon PoS Amoy1~20 seconds
Solana Devnet32~25 seconds


Block confirmations for L2s to Ethereum

Arbitrum, Base, and OP Mainnet are L2 blockchains that publish transaction data to their L1 blockchain, Ethereum. Before attesting to CCTP messages in an Ethereum block, Circle waits for the Ethereum block to finalize, which requires at least 65 block confirmations.


Block confirmations for Polygon PoS

We have currently set our time-to-attestation at 200 blocks for events on Polygon PoS mainnet. Deterministic finality (PIP-11) was rolled out on Polygon PoS mainnet in 2023, and we may reduce our time-to-attestation time as we observe PIP-11's performance.