Blockchain Confirmations

Each time a new block is added to a blockchain, it confirms the previous blocks.

Without a sufficient number of confirmations, transactions may be changed by blockchain reorganization, or reorg. Reorgs occur when validators discard one or more blocks and replace them with a different set of blocks, rewriting part of the chain.

Each additional block confirmation added after a block makes that block less likely to be removed in a reorg. Each confirmation adds confidence that the transaction is permanent.

Confirmations show how safe a transaction is from reorg. The confirmation number is how many blocks must be added until a block is considered permanent.

Each chain's confirmation number is different, and determined by Circle. Confirmation numbers are based on a variety of factors, including the chain's history, potential for reorg, and overall network architecture.

For L2 chains, Circle waits for blocks on the L1 chain. This happens after the L2 block gets included in an L1 block.

When an incoming transfer is included in a block, the API makes it available for you. However, the transfer remains in the running status. It won't credit the balance of the associated wallet with the transfer amount until the required number of confirmations has been reached.

Once the confirmation number is reached, the transfer status changes to completed. If you subscribed to webhook notifications, you'll get a message about this change.

You can use transfers in your processes before they reach completed status. This comes with risk. Chain reorgs are rare, but they can happen. If you use transfers before they get enough confirmations, you take on this risk.