The first confirmation records the transaction
A transaction receives its first confirmation when it appears in a block on the best valid chain known to a node. Each block built above it adds another confirmation.
An unconfirmed transaction may be valid and widely relayed, but it is not yet protected by accumulated proof-of-work in the blockchain.
Bitcoin finality is probabilistic
Two valid blocks can occasionally be discovered near the same time. Nodes converge on the valid chain with the most accumulated proof-of-work, leaving the other block stale.
This is a chain reorganisation. A transaction removed from a stale block may return to mempools or conflict with a transaction in the replacement chain.
Wait according to risk
Every additional confirmation makes changing the transaction's history progressively more difficult. No one confirmation number suits every payment.
Low-value payments may tolerate less waiting. High-value or irreversible delivery should use a more conservative policy based on value and counterparty risk.
Visual recap
Confidence accumulates above a transaction
A payment enters a block and becomes more deeply buried as valid blocks are added.
Broadcast
Block inclusion
1 confirmation
More blocks
More proof-of-work
Higher confidence
Key takeaways
- One confirmation means inclusion in the current best chain.
- Bitcoin provides probabilistic rather than instant absolute finality.
- Short reorganisations can happen without an attack.
- Confirmation policy should reflect payment value and risk.
Lesson recap
Check what you learned
Reveal each model answer, then honestly mark whether you understood it or need another review.
1 of 3
Recall
Why does confidence generally increase with each confirmation?
References
