Consensus rules

This page lists the rules of the bitcoin consensus value, in the order that validation runs them. The #:rule of a rejection is one of these names, or one of the script rules below.

Rule	Scope	Description
inputs-nonempty	tx	A transaction spends at least one coin.
outputs-nonempty	tx	A transaction creates at least one output.
output-range	tx	Every output amount, and their total, lies between 0 and 21M BTC.
duplicate-inputs	tx	No coin is spent twice by one transaction.
locktime-final	tx	A transaction with nLockTime set waits until a block above that height, unless every input's nSequence is final.
input-exists	input	Each input spends an unspent coin on this chain.
coinbase-maturity	input	A coinbase output is spendable once it is 100 blocks deep.
value-balance	tx	The sum of the inputs is equal to or more than the sum of the outputs. The difference is the fee.
sequence-lock	input	BIP68: an input whose nSequence encodes a relative lock waits that many blocks after its coin confirmed.
witness-script	input	Each input's witness satisfies the script of the coin it spends.

Script rules

A failure of witness-script gives the name of a more specific rule: one of these rules, or the opcode that failed (see opcodes).

Rule	Description
bad-opcode	The script uses an opcode that this consensus does not define.
cleanstack	A segwit script must stop with exactly one item on the stack.
eval-false	The script stopped with false on top of the stack, for example after a CHECKSIG with a signature that is not valid. #:cause gives the cause.
key-path-sig	A taproot spend through the key path must have a valid signature by the internal key. #:cause gives the cause.
stack-underflow	An opcode needed more stack items than the stack had.
taproot-commitment	The control block and the leaf script do not commit to the taproot output key.
unbalanced-conditional	The IF, ELSE and ENDIF opcodes do not match.
unsupported	The model does not have this feature yet, for example locks based on time.
unsupported-spend	The model does not have this type of output yet.
witness-program-mismatch	The witness does not agree with the witness program of the output: the number of items is wrong, or the hash of the script is not the program.

Proposal rules

Rule	Opcode	Description
ctv-template-mismatch	ctv	The tx that spends the coin does not agree with the CTV template. #:fields gives the fields that are different. #:expected and #:got give the values of the template and of the tx.