OP_RETURN

OP_RETURN is a script opcode used to terminate the script and return the top value on the stack. This opcode is analogous to the return function in programming languages. The OP_RETURN opcode has a controversial history in Bitcoin and as a result has been primarily used as a means of storing data on the block chain.

OP_RETURN Functionality

OP_RETURN terminates the script leaving the stack as-is and letting the result on top of the stack determine the success or failure of the script. Note that if the top stack is non-empty and non-zero (zero including a string of zeros, of zero bytes), then it is considered as successful. Otherwise, it is considered as fail. OP_RETURN can be used in combination with flow control opcodes to implement branching, conditional logic in scripts.

Example

The below script is a metanet node that attaches the Metanet data to a UTXO with funds. This can be used to ensure that metanet nodes are left in the UTXO set

𝑇𝑥𝐼𝐷𝑛𝑜𝑑𝑒
Inputs	Outputs
<sigmetaParent> <pubKeymetaParent> <sigscript> <pubKeyscript>	DUP HASH160 <pkhscript> EQUALVERIFY CHECKSIG RETURN <meta> <pkmetaNode> <txidmetaParent>