Block time

Block time is the average interval between new blocks on a blockchain. It determines how quickly a transaction can get its first confirmation and how fast the ledger grows.

Bitcoin targets 10 minutes per block, kept on track by the difficulty adjustment, although individual blocks can arrive seconds or more than an hour apart because mining is random. Litecoin targets 2.5 minutes. Ethereum, since moving to proof of stake, produces blocks in fixed 12-second slots. Solana aims for slots of roughly 400 milliseconds.

Shorter block times feel faster to users but have costs. Blocks must travel across the global network before the next one is found; if they come too quickly, more competing blocks are created, which wastes work and can favour large, well-connected miners. That is why Bitcoin keeps a long block time and pushes fast payments to layer 2 networks like Lightning. Block time is also different from finality, the point at which a transaction is practically irreversible.