11 - nSequence

The nSequence field is a 4 byte little endian number that is the sequence number of the input. This value can be used with nLocktime to put transactions into a non-final state, allowing a managed transfer of data to take place.

Example: Extract and check nSequence

In this example, we will extract the nSequence value of this input and only allow the UTXO to be spent if it is final.

Stack	Script	Description
<r_tx_preimg>	...	Version, hash_prevouts, hash_nSequence, hash_outpoints, script and value have been removed
<r_tx_preimg>	OP_4	nSequence length is 4 bytes long
<r_tx_preimg> 0x04	OP_SPLIT	Split nSequence
<nsequence> <rr_tx_preimg>	OP_SWAP	Move to top of stack
<rr_tx_preimg> <nsequence>	0xFFFFFFFF	0xFFFFFFFF is final
<rr_tx_preimg> <nsequence> 0xFFFFFFFF	OP_EQUALVERIFY	Fail script if tx is non-final
<r_tx_preimg>	...	rest of script