OP_RETURN
A script opcode commonly used to create a provably unspendable output carrying a limited data payload.
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.
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.
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
Explore connected entries beyond the alphabetical index.
Opcode
→An encoded instruction interpreted by a virtual machine or transaction script engine.
Transaction
→A serialized state transition that a blockchain can validate, relay, and include in a block.
Unspent Transaction Output (UTXO)
→A discrete spendable output on a UTXO blockchain, similar to a digital coin that must be spent whole.
Protocol
→The formal set of rules that define how participants in a network communicate and reach consensus.