OP_RETURN
technical · blockchain
A script opcode commonly used to create a provably unspendable output carrying a limited data payload.
1.general
OP_RETURN immediately makes the executed output script fail, so an output using it is provably unspendable and does not need to remain in the spendable UTXO set. Standard transaction formats can place a limited data payload after the opcode.
2.policy
Relay limits for data size, number of outputs, and accepted script forms are node-policy choices and have changed across networks and software versions. Consensus validity and standard relay acceptance are not the same.
3.uses
Timestamping, protocol markers, and legacy token systems have used OP_RETURN. The data is public and replicated with chain history, so applications should minimize it and avoid personal information or large content.
Related terms
Opcode
→An encoded instruction interpreted by a virtual machine or transaction script engine.
technical · scripting
Transaction
→A record submitted to a blockchain to make a payment or another permitted change.
blockchain · technical
Unspent Transaction Output (UTXO)
→A discrete spendable output on a UTXO blockchain, similar to a digital coin that must be spent whole.
technical · blockchain
Protocol
→The formal set of rules that define how participants in a network communicate and reach consensus.
blockchain · networking
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