A OP_RETURN -debat flared up in the Bitcoin industry in recent weeks and has now invaded most conversation sites in the industry. The topic is rich and complex, and many people have strong opinions about the matter.
OP_RETurn is an OPCODE in Bitcoin’s scripting language used to store metadata or arbitrary data that are not relevant to Bitcoin transaction validation, as such can be cropped by node runners without much problems, allowing more effective control of spam, while also providing developers a controlled environment to anchor data about chain.
By taking a damage reduction method for the spam problem, the OP_RETURT -Turn -Controvers were recently triggered by a pull request submitted by Peter Todd to the Bitcoin Core archive. Supporters of the update seek to eliminate the amount of arbitrary data that can be placed in the OP_Retur by removing the Mempool policy rule that limits it to 80 bytes. As a consequence, this border moves up to the consensus block size hood of 1MB non-Segwit data. They claim that this limit is no longer effective in stopping spam and, on the contrary, leads to more harmful behavior, such as filling data in Utxos, which harms node runners.
In addition, the proposal removed the data carrier flag, a configuration setting that allowed node runners to choose which transactions should be filtered from their local MEMPOOL based on how much arbitrary data up_return transported.
The opposition, led by Luke Dashjr, not only wants to keep up_return boundary in place and retain the data carrier size, but proposes further MEMPOOL policy restrictions for arbitrary data and “non-monetary” transactions on Bitcoin.
Both camps generally agree that arbitrary data about Bitcoin is a bad thing for the network. They also agree that filters cannot possibly filter all kinds of spam. What they disagree with is how effective these kinds of filters are in mitigating spam. They also disagree on the consequences of imposing or removing these filters from the network, their influence on the cost of running a knot and their influence on mining centralization.
The Author’s Note: Of course, not all advocates of the OP_Ret tour changes agree with all the arguments in favor of the pull request, and not all opponents agree with all the arguments against it. This is just a general (and probably incomplete) overview of the different arguments out there.
Left by Peter Todd, although supported by many Bitcoin core grants, the Removal of the OP_Return boundary represents a damage reduction method to the problem of spam and arbitrary data about Bitcoin.
Todd claims that the current OP_Return boundary, originally placed over a decade ago to give spammers a secure and controlled space for arbitrary data, no longer serves its purpose as companies and enthusiasts has developed direct-to-Min-Private Mempools, such as Mara’s slipstream, BYPASS MEMPOBOL policy.
The Op_return boundary was introduced after Satoshi Nakamoto left to protect the network from similar spam, but in a very different era where blocks were rarely full, much less boasting of a high-fee environment. There were also few for no pruning tools and the software was very ineffective. Many optimizations have been implemented in the last decade and their cumulative effects affect this debate.
Thus, the OP_RETurn boundary was more effective once it was created and more difficult to bypass. Today, NFT and arbitrary data enthusiasts with ambitious projects have squeezed out of the OP_RETROUR space at the current Mempool limit, resorting to filling arbitrary data in the UTXO set instead. Unlike up_return or Segwit room, which can reasonably be pruned by nodes, the UTXO set is generally kept in RAM, the most expensive form of memory. The UTXO set must be treated by nodes to verify the supply of coins and be able to validate the integrity of new transactions, a basic piece of driving a knot, without which home nodes lose much of their value proposition. UTXO data, which is filled as a result, imposes significant costs for node runners by increasing the initial block -down, total synchronization time and hardware requirements that ultimately damage the decentralization of the Bitcoin network.
Finally, supporters claim that miners are “rational economic actors”, an economic term, which means that in order to stay alive in a very competitive market, miners have to optimize for profits where possible. So if mining consensus-value-not-standard transactions give them an advantage they will take it.
Back in 2023, Luke Dashjr suggested a change that tried to apply data carrier MEMPOOL policy on Segwit and Taproot arbitrary data, such as inscriptions, further limiting the options for spammers. Peter Todd opposed PR and explained that “the transactions targeted after this Pull request are a very significant source of fee income for miners. It is very unlikely that miners will give up this source of income. Censoring these transactions will simply encourage the development of private MEPOLs – harmful to small miners – while they make a fee less.”
Todds Pull request did one more thing except removing up_return boundary: It also removed the data carrier flag from the configuration settings for node operators. Users of Bitcoin Core Node Software can control which transactions they forward through their knot based on a configuration option called DataCarrier flag that specifically looks at the amount of data inside OP_RETurn, with standard being 80 bytes of arbitrary data.
Supporters claim that the flag is outdated now and that the occurrence of tools such as Mining Pool Mara’s slipstream program or Todds Libre relay streamlining the inclusion of consensus-valid transactions, even if they are “non-standard” of the MEMPOOL policy.
Consensus-Valid-not-standard transactions are in conflict with Mempool policy rules such as up_return boundary, but do not break any consensus rules and can therefore be included in Bitcoin by a miner directly if the miner can simply be made aware of the transaction. Such systems already outdated controversial filters claim supporters, making the data carrier -flag irrelevant, especially if the Standardop_return size limit is lifted.
Supporters claim that the flag only gives users the illusion of control and is a “footgun” – a tool that is dangerously easy to abuse – and in this case does not need the user.
Finally, removal of the data carrier flag together with the OP_Return boundary can remove a recurring point of conflict and controversy for the Bitcoin core, as filter-supporting Bitcoin maximalists are not the only ones with an opinion on the matter or able to gather the Internet to oppose a pull request.
By 2023, a pull request was requested to the Bitcoin core, which tried to change the Standard Mempool policy on the routing of multisig transactions. This is an old standard used today by NFT protocols such as stamps, including to ensure that their arbitrary data easily makes it the chain and even better cannot be easily cropped. The wooden request was quickly transferred to an Internet flame war between “Spammers” and supporters of the change and paused its integration into the Bitcoin core in a similar way that Todds Pull request did last week.
By removing the data carrier flag, which supporters claim, is irrelevant anyway, drama of this kind can be put to bed, and the Bitcoin core contributions can move on to other, more pressing problems, they claim.
The opposition-in community known as the filters-and-led by long-lasting Bitcoin core contributors Luke Dashjr claims that the removal of up_return size is a surrender to spammers that perfect filters are not what is needed, rather that the mere action of filtering sends a message to companies or projects that wish to build up Bitocin. The message is: Go to build it somewhere else or find a better way to do it.
They claim that Bitcoin is only a network for monetary transactions that everything outside this definition is spam. In their opinion, monetary transactions are Bitcoin transactions that only seek to transfer Bitcoin-denomined value between two users, with goods and services transferred off-chain in return.
According to Chris Guida, a lightning developer and Bitcoin Knots supporter, there are about two formal definitions of monetary transactions on Bitcoin.
“I think there are effectively two different definitions: one has to deal with whether the transaction actually uses Bitcoin as a payment rail, and not a database for fraud ‘products’,” with reference to NFTs, added “and the other definition is effective,” it fits within 40/80 Bytes’ in OP_RETurn. If none of these standards apply, they consider spam. “
NFT -trading or arbitrary data used to anchor layer 2 protocols on top of Bitcoin does not count as monetary transactions in this sense and thus considered spam, although these layers 2 may make financial transactions of different kinds.
Furthermore, filters claim that the Bitcoin core must be actively looking for ways of deterring this kind of behavior. They claim that spammers moving to UTXO filling are proof that filters are working as the pressure effectively leads them to find other ways to spam the network. In other words, if filters did not work, spammers would not be looking for more expensive terrain to build their spam systems, such as UTXO sets.
Thus, not only the up_return border must be kept, but it should probably be scrambled further, perhaps back to the historic 40 bytes. Furthermore, the data carrier flag must be expanded to manage separate witness and taprot transactions that are not closed to arbitrary data up to the block size limit and utilized by spammers whose most prominent are inscriptions.
Finally, the filters confirm that systems such as Todd’s Libre Relay or Maras Slipstream can be fought in different ways, and they do not intend to fold only if Bitcoin Core continues with its current development path. The result has been a growing interest in Bitcoin Knots, including the alternative implementation of Bitcoin maintained by Luke Dashjr to allow Bitcoin users to run their own filters as they find appropriate and fight spam. From the time of writing and according to LUK’s network analysis, over 5% of the Bitcoin nodes run Bitcoin knob.
Filterers and Bitcoin knob enthusiasts also defend the data career flag in principle. They claim that coordinated node runners with sufficient numbers have a path to successfully filter a particular set of spam that goes so far as to argue for the expansion of what the data carrier flag controls, as seen in this wooden arrest from 2023 by Luke Dashjr. In that, Segwit and Taproot arbitrary data storage functions would also be limited by nodes-controlled data carrier flags; They are not at the moment.
In particular, this point has resonated with many people, as seen by the growing number of Bitcoiners running the Bitcoin Knots implementation of Bitcoin, which includes Mempool -Political changes of this kind, while all other Bitcoin core code is intact.
Some Bitcoin-Knob’s supporters, like Chris Guida, are starting to talk about user-controlled relay policies or “modular filters” that can be created from refactoring MEMPOOL policy code and updated to follow certain actively managed templates-a kind of automated spam filteralgorithm that users could activate from a provider.
At X he argued “It is often argued that filtration of spam is a” cat-and-mouse game “where the filters are somehow in a disadvantage.
I think it’s absurd. We can create filters as fast as new fungible token metaprotocols can create their new TX formats before they even hit the mainnet. “
While even filters recognize that there are limits to spam control, they maintain that a hostile environment for spam-related software systems and business models is a good thing and one that needs to be maintained to deter bad behavior, even if the more price-pursuing versions will nevertheless go directly to miners and pay to make it a block.