This section has been updated to Bitcoin Core @ v23.0

One of the fundamental concepts underlying bitcoin is that nodes on the network are able to maintain decentralized consensus on the ordering of transactions in the system.

The primary mechanism at work is that all nodes validate every block, and every transaction contained within that block, against their own copy of the consensus rules. The secondary mechanism is that in the event of a discrepancy between two competing chain tips nodes should follow the chain with the most cumulative proof-of-work. The result is that all honest nodes in the network will eventually converge onto a single, canonical, valid chain.

If all nodes do not compute consensus values identically (including edge cases) a chainsplit will result.

For more information on how the bitcoin networks' decentralized consensus mechanism works see the Mastering Bitcoin section on decentralized consensus.

In Bitcoin Core there are an extra level of validation checks applied to incoming transactions in addition to consensus checks called "policy" which have a slightly different purpose, see consensus vs policy for more information on the differences between the two.

A collection of functions and variables which must be computed identically to all other nodes on the network in order to remain in consensus and therefore on the main chain.


Validation of blocks, transactions and scripts, with a view to permitting them to be added to either the blockchain (must pass consensus checks) or our local mempool (must pass policy checks).

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