// GLOSSARY -- BLOCKCHAIN & CRYPTO FUNDAMENTALS
What is Block Confirmation?
A block confirmation is the inclusion of a transaction in a mined/validated block, with each subsequent block adding additional confirmation — increasing confidence that the transaction won't be reversed.
WHY IT MATTERS
When your transaction is included in a block, that's one confirmation. Each subsequent block adds another confirmation. More confirmations = less likely the transaction can be reversed through a chain reorganization.
For PoW chains (Bitcoin), each confirmation adds security exponentially — the cost to reverse 6 confirmations is immense. For PoS chains (Ethereum), economic finality (~15 minutes) provides a definitive guarantee.
Different applications require different confirmation counts based on the value at risk.
FREQUENTLY ASKED QUESTIONS
How many confirmations should I wait?
Low value: 1 confirmation. Medium value: 12 confirmations (~2.5 min on Ethereum). High value: wait for finality (~15 min). Bitcoin standard: 6 confirmations (~60 min).
What is a chain reorganization?
When a competing chain of blocks replaces the current one, removing some recent transactions. Deeper confirmations are harder to reorganize. This is why exchanges wait for multiple confirmations.
Do L2s have confirmations?
L2s provide instant soft confirmations from the sequencer. Full security requires the data to be posted and finalized on L1 — inheriting L1's confirmation/finality model.