OP RETURN: Difference between revisions

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== OP_RETURN prefixes ==
== 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! Protocols with no prefix do not use a prefix in OP_RETURN transactions.
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. Protocols with no prefix do not use a prefix in OP_RETURN transactions.
 
{| class="wikitable"
|-
! Prefix !! Protocol
|-
|    || [https://play.google.com/store/apps/details?id=a.apkt Apekato]
|-
| SPK || [http://coinspark.org/developers/ CoinSpark]
|-
| DOCPROOF || [http://www.proofofexistence.com/ Proof of Existence]
|-
| CryptoTests- || [http://crypto-copyright.com/ Crypto Copyright]
|-
| CryptoProof- || [http://crypto-copyright.com/ Crypto Copyright]
|-
| 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]
|-
| BID || [http://bitpos.me/ Identity]
|}


== External resources on OP_RETURN ==
== External resources on OP_RETURN ==

Revision as of 02:05, 7 May 2017

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 burn bitcoins.

Currently, the default Bitcoin client relays OP_RETURN transactions up to 80 bytes [1], 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, the use of OP_RETURN continues unabated: while there is no global miner consensus to stop people from embedding arbitrary data in the blockchain if they want to, OP_RETURN is somewhat more efficient in terms of 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. Discussion on GitHub pull request

The creation of OP_RETURN outputs also destroys Bitcoins used in the outputs of OP_RETURN transactions, which contributes to future deflationary pressures.

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 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.

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. Protocols with no prefix do not use a prefix in OP_RETURN transactions.

External resources on OP_RETURN

Viewing OP_RETURN

Explaining OP_RETURN

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