Block time sets the rhythm of a network: how long a transaction waits before its first confirmation, and how quickly the chain accumulates the depth that makes a transaction hard to reverse. Bitcoin targets about ten minutes, many newer chains target seconds, and proof-of-work networks hold the target steady by adjusting difficulty as hash rate changes.
Shorter is not simply better. Fast blocks reach users sooner but increase the chance that two valid blocks are produced almost simultaneously and one is discarded, and they grow the ledger faster, which raises the cost of running a node. The choice is a trade between responsiveness and the decentralisation that cheap node operation supports.
How many confirmations does a transaction need?
It depends on the value and the chain's block time. Exchanges commonly wait for a number of blocks that represents a comfortable span of time rather than a fixed count, since deeper burial is what makes reversal impractical.
Last updated October 17, 2026