Difference between revisions of "OP RETURN"

From Bitcoin Wiki
Jump to: navigation, search
(Add quote from Bitcoin 0.9.0 release)
(The recommendation for BIPs is outdated. No such BIPs exist and the practice has been discouraged on the mailing list.)
(19 intermediate revisions by 8 users not shown)
Line 1: Line 1:
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 transaction by following the OP_RETURN with an OP_PUSHDATA. Since any outputs with OP_RETURN are provably unspendable, OP_RETURN outputs can be used to [[Proof of burn|burn]] bitcoins.
+
'''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? ==
 
+
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.
== Philosophy ==
 
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]
 
  
 
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]:
Line 13: Line 11:
 
</blockquote>
 
</blockquote>
  
== Resources on OP_RETURN ==
+
== OP_RETURN applications ==
* [http://coinsecrets.org/ coinsecrets.org]: An OP_RETURN transaction explorer
+
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 [[stealth address]]).
* [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]
 
  
== 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]
 
|-
 
| 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]
 
|}
 
 
{{DISPLAYTITLE:OP_RETURN}}
 
{{DISPLAYTITLE:OP_RETURN}}

Revision as of 15:30, 20 September 2018

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 stealth address).