Finality and block confirmations

Block confirmation requirements and attestation timing for CCTP

Before signing an attestation, Circle waits for blockchain transactions to achieve the appropriate level of transaction finality. The required finality level depends on whether you use Fast Transfer or Standard Transfer.

• Fast Transfer: Attestations are issued after the transaction is confirmed and included in a block, typically in seconds. Because of the faster finality time, Fast Transfers are subject to a global allowance to mitigate reorganization risks.
• Standard Transfer: Attestations are issued after hard finality, when the transaction is unlikely to be reversed by a chain reorganization, typically in minutes.

Fast Transfer attestation times

The table below shows the average time for attestations to become available when using Fast Transfer (minFinalityThreshold ≤ 1000):

Source blockchain	Block confirmations	Average time
Ethereum	2	~20 seconds
Arbitrum	1	~8 seconds
Base	1	~8 seconds
Codex	1	~8 seconds
EDGE	1	~8 seconds
Ink	1	~8 seconds
Linea	1	~8 seconds
Morph	1	~8 seconds
OP Mainnet	1	~8 seconds
Plume	1	~8 seconds
Solana	2-3	~8 seconds
Starknet	4	~20 seconds
Unichain	1	~8 seconds
World Chain	1	~8 seconds

Blockchains without Fast Transfer:

Some blockchains don’t support Fast Transfer as a source blockchain because their standard attestation times are already fast. For those CCTP supported blockchains where Fast Transfer is disabled as a source, use Standard Transfer instead.

Standard Transfer attestation times

The table below shows the average time for attestations to become available when using Standard Transfer (minFinalityThreshold ≥ 2000):

Source blockchain	Block confirmations	Average time
Ethereum	~65	~15-19 minutes
Arbitrum	~65 ETH blocks	~15-19 minutes
Arc	1	~0.5 seconds
Avalanche	1	~8 seconds
Base	~65 ETH blocks	~15-19 minutes
BNB Smart Chain	3	~2 seconds
Codex	~65 ETH blocks	~15-19 minutes
Cronos	1	~0.5 seconds
EDGE	~65 ETH blocks	~16-21 minutes
HyperEVM	1	~5 seconds
Injective	1	~0.65 seconds
Ink	~65 ETH blocks	~30 minutes
Linea	1	~6-32 hours
Monad	1	~5 seconds
Morph	~65 ETH blocks	~20-30 minutes
OP Mainnet	~65 ETH blocks	~15-19 minutes
Pharos	1	~7 seconds
Plume	~65 ETH blocks	~15-19 minutes
Polygon PoS	2-3	~8 seconds
Sei	1	~5 seconds
Solana	32	~25 seconds
Sonic	1	~8 seconds
Starknet	~65 ETH Blocks	~4 to 8 hours
Stellar	1	~5 seconds
Unichain	~65 ETH blocks	~15-19 minutes
World Chain	~65 ETH blocks	~15-19 minutes
XDC	3	~10 seconds

Layer 2 finality

Layer 2 (L2) blockchains built on Ethereum publish transaction data in batches to Ethereum Layer 1. The finality characteristics of L2 chains depend on when batches are posted and when those batches achieve finality on Ethereum L1.

OP Stack chains

OP Stack-based chains (including Base, OP Mainnet, and World Chain) post state updates using EIP-4844 blob transactions approximately every 15 minutes. Circle waits for the Ethereum L1 block containing the batch to finalize, which typically takes ~65 blocks (15-19 minutes) after the batch is posted.

Linea

Linea has a longer finality period compared to other L2 chains. Standard Transfer on Linea typically requires 6-32 hours before attestations become available.

Starknet

The typical time to reach hard finality on Starknet is 4–8 hours, as finality depends on when the zk-rollup proof is posted to Ethereum and when its corresponding L1 block finalizes.

Solana finality

Solana uses a different finality model:

Fast Transfer

Circle waits for the block to be confirmed (votes from validators representing over two-thirds of total stake). This typically takes 2-3 blocks (~8 seconds).

Standard Transfer

Circle waits for block finality, which takes 32 blocks (~25 seconds).