Difference between revisions of "OP RETURN"

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'''OP_RETURN''' is a [[script]] opcode used to mark a transaction output as invalid. Since the data after OP_RETURN are irrelevant to Bitcoin payments, arbitrary data can be added into the output after an OP_RETURN. Since any outputs with OP_RETURN are provably unspendable, OP_RETURN outputs can be used to [[Proof of burn|burn]] bitcoins.
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'''OP_RETURN''' is a [[script]] opcode used to mark a transaction output as invalid. Since any outputs with OP_RETURN are provably unspendable, OP_RETURN outputs can be used to [[Proof of burn|burn]] bitcoins.
 
 
Currently, the default Bitcoin client relays OP_RETURN transactions up to 80 bytes [https://github.com/bitcoin/bitcoin/search?utf8=%E2%9C%93&q=MAX_OP_RETURN_RELAYa], but does not provide a way for users to create OP_RETURN transactions.
 
  
 
== Is storing data in the blockchain acceptable? ==
 
== Is storing data in the blockchain acceptable? ==
Some members of the Bitcoin community believe that use of OP_RETURN violates the contract of Bitcoin, because Bitcoin was intended to provide a record for financial transactions, not a record for arbitrary data. Despite this, use of OP_RETURN may continue unabated because there is no easy way to stop people from embedding arbitrary data in the blockchain if they want to, and OP_RETURN is reasonably efficient in terms of [http://i.imgur.com/VAGZWBK.png data bytes stored as a fraction of blockchain space consumed]. Compared to some other ways of storing data in the blockchain, OP_RETURN has the advantage of not creating bogus UTXO entries. [https://github.com/bitcoin/bitcoin/pull/5286 Discussion on GitHub pull request]
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Many members of the Bitcoin community believe that use of OP_RETURN is irresponsible in part because Bitcoin was intended to provide a record for financial transactions, not a record for arbitrary data. Additionally, it is trivially obvious that the demand for external, massively-replicated data store is essentially infinite. Despite this, OP_RETURN has the advantage of not creating bogus [[UTXO]] entries, compared to some other ways of storing data in the blockchain.
  
 
From [https://bitcoin.org/en/release/v0.9.0#opreturn-and-data-in-the-block-chain Bitcoin Core release 0.9.0]:
 
From [https://bitcoin.org/en/release/v0.9.0#opreturn-and-data-in-the-block-chain Bitcoin Core release 0.9.0]:
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== OP_RETURN applications ==
 
== OP_RETURN applications ==
OP_RETURN is used for writing human-language messages, digital asset proof-of-ownership, and storing data. Its use has been proposed for P2P application discovery. See the "prefixes" table below.
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OP_RETURN can be used for digital asset proof-of-ownership, and has at times been used to convey additional information needed to send transactions (see [[ECDH address]]).
 
 
== OP_RETURN prefixes ==
 
Often, OP_RETURN transactions include a prefix to identify which protocol they belong to. There is no standardized method of claiming OP_RETURN prefixes, and not all OP_RETURN transactions use prefixes. At the time of writing, this wiki page is probably the most complete list of OP_RETURN prefixes. Note that this table is an attempt to catalog OP_RETURN prefixes that are already in use, *not* a system for reserving OP_RETURN prefixes!
 
 
 
{| class="wikitable"
 
|-
 
! Prefix !! Protocol
 
|-
 
| SPK || [http://coinspark.org/developers/ CoinSpark]
 
|-
 
| DOCPROOF || [http://www.proofofexistence.com/ Proof of Existence]
 
|-
 
| CryptoTests- || [http://crypto-copyright.com/ Crypto Copyright]
 
|-
 
| CryptoProof- || [Crypto Copyright http://crypto-copyright.com/
 
|-
 
| BS || [http://blocksignit.com/ BlockSign]
 
|-
 
| OA || [https://github.com/OpenAssets/open-assets-protocol/blob/master/specification.mediawiki Open Assets]
 
|-
 
| STAMPD## || [http://stampd.io/ stampd]
 
|-
 
| Factom!! || [http://factom.org/ Factom]
 
|-
 
| FACTOM00 || [http://factom.org/ Factom]
 
|-
 
| Fa || [http://factom.org/ Factom]
 
|-
 
| FA || [http://factom.org/ Factom]
 
|-
 
| tradle || [http://tradle.io/ Tradle]
 
|-
 
| LaPreuve || [http://www.lapreuve.net/ LaPreuve]
 
|-
 
| hex:5888 || [http://blog.onename.com/blockstore-bitcoin/ Blockstore]
 
|-
 
| hex:5808 || [http://blog.onename.com/blockstore-bitcoin/ Blockstore]
 
|-
 
| id || [http://blog.onename.com/blockstore-bitcoin/ Blockstore]
 
|-
 
| BITPROOF || [https://bitproof.io/ Bitproof]
 
|-
 
| S1 || [https://stampery.co/ Stampery]
 
|-
 
| S2 || [https://stampery.co/ Stampery]
 
|-
 
| S3 || [https://stampery.co/ Stampery]
 
|-
 
| S4 || [https://stampery.co/ Stampery]
 
|-
 
| S5 || [https://stampery.co/ Stampery]
 
|-
 
| ASCRIBE || [https://www.ascribe.io/ Ascribe]
 
|-
 
| ProveBit || [https://github.com/thereal1024/ProveBit ProveBit]
 
|-
 
| EW  || [http://eternitywall.it/ Eternity Wall]
 
|-
 
| CC || [http://colu.co/ Colu]
 
|-
 
| omni || [http://www.omnilayer.org/ Omni Layer]
 
|-
 
| MG || [http://monegraph.com/ Monegraph]
 
|-
 
| RMBd || [https://app.remembr.io/ Remembr]
 
|-
 
| RMBe || [https://app.remembr.io/ Remembr]
 
|-
 
| ORIGMY || [http://originalmy.com/ OriginalMy]
 
|}
 
  
== External resources on OP_RETURN ==
 
=== Viewing OP_RETURN ===
 
* [http://coinsecrets.org/ coinsecrets.org]: An OP_RETURN transaction explorer]
 
* [http://bitcoinstrings.com/ bitcoinstrings.com]: A site showing raw strings in Bitcoin transactions
 
  
=== Explaining OP_RETURN ===
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{{DISPLAYTITLE:OP_RETURN}}
* [https://github.com/coinspark/python-OP_RETURN python-OP_RETURN]
 
* [http://bitcoin.stackexchange.com/questions/29554/explanation-of-what-an-op-return-transaction-looks-like StackExchange: Explanation of what an OP_RETURN transaction looks like]
 
* [http://www.slideshare.net/coinspark/bitcoin-2-and-opreturns-the-blockchain-as-tcpip Metadata in the Blockchain: The OP_RETURN Explosion]
 
* [http://wlangiewicz.com/blog/2014/10/24/how-to-put-custom-messages-into-bitcoin-blockchain-op-return/ How to Put Custom Messages Into Bitcoin Blockchain - OP_RETURN]
 

Latest revision as of 12:54, 27 June 2020

OP_RETURN is a script opcode used to mark a transaction output as invalid. Since any outputs with OP_RETURN are provably unspendable, OP_RETURN outputs can be used to burn bitcoins.

Is storing data in the blockchain acceptable?

Many members of the Bitcoin community believe that use of OP_RETURN is irresponsible in part because Bitcoin was intended to provide a record for financial transactions, not a record for arbitrary data. Additionally, it is trivially obvious that the demand for external, massively-replicated data store is essentially infinite. Despite this, OP_RETURN has the advantage of not creating bogus UTXO entries, compared to some other ways of storing data in the blockchain.

From Bitcoin Core release 0.9.0:

This change is not an endorsement of storing data in the blockchain. The OP_RETURN change creates a provably-prunable output, to avoid data storage schemes – some of which were already deployed – that were storing arbitrary data such as images as forever-unspendable TX outputs, bloating bitcoin's UTXO database.

Storing arbitrary data in the blockchain is still a bad idea; it is less costly and far more efficient to store non-currency data elsewhere.

OP_RETURN applications

OP_RETURN can be used for digital asset proof-of-ownership, and has at times been used to convey additional information needed to send transactions (see ECDH address).