On May 6, 2025, a small group of Bitcoin developers unexpectedly attempted to change Bitcoin Core's default mempool policy – the dominant software for full nodes – by proposing to raise the data storage limit of OP_RETURN, leading to a controversy known as the 'OP_RETURN war.' Is this an effort to reduce harm or does it hide business interests? Let’s analyze in detail.
The OP_RETURN War: Surprising Proposal and Strong Reactions
Last week, a group of developers quietly proposed pull request (PR) 32359, drafted by Peter Todd, aimed at increasing the data storage capacity of OP_RETURN – an opcode in Bitcoin that allows embedding non-financial data. This proposal, which had previously failed in 2023, faced fierce criticism before merging into the mainnet. Mononaut joked that it resembled a 'fork #bitcoin for quantum resistance' that bypassed the mailing list and BIP process, jumping straight into production. Critics labeled the PR as 'chaotic,' 'crazy,' 'deceptive,' 'lacking consensus,' and even 'subversive,' while supporters argued that it standardizes mempool policies and modernizes transactions.
Ultimately, concerns about censoring opposing viewpoints, reducing Bitcoin's financial role, and hidden business interests prevented PR 32359 from merging.
'Reducing Harm' Motivation: A Developer's Perspective
The supporters, pushed into a defensive position, reframe their actions as a long-term 'reducing harm' effort for Bitcoin. They argue that embedding large data via OP_RETURN merely standardizes a popular reality: users have stored text, images, programming code, and non-financial data in unconventional parts of Bitcoin blocks, such as Taproot outputs, even taking advantage of SegWit discounts to reduce storage costs. The 83-byte limit of OP_RETURN has become outdated as other options exist.
Mark 'Murch' Erhardt from Chaincode Labs explained on StackerNews that raising the OP_RETURN limit would allow entities like Citrea – a venture-backed Bitcoin project – to operate more efficiently without forcing full nodes to load and validate large unprunable UTXO. Peter Todd, the author of the PR at the request of Antoine Poinsot from Chaincode, confirmed: 'I was asked by a Core developer to open the PR because entities like Citrea use unprunable UTXO instead of OP_RETURN due to size limitations.'
Citrea and the Controversy of Business Interests
Citrea needs to embed a 100-byte data package – 17 bytes larger than the OP_RETURN limit – for its operation. However, due to restrictions, Citrea writes directly into the unspent set #UTXO , increasing the number of UTXO and putting a heavy load on full nodes. Supporters argue that raising the OP_RETURN limit will 'reduce harm' by replacing this method. Jameson Lopp, a Citrea investor and supporter of PR 32359, denies any conflict of interest, stating: 'Citrea's protocol does not benefit from this change! We merely suggest they use OP_RETURN to avoid bloating UTXO.'
Consequences and Ongoing Conflict
The change of Bitcoin Core's important default value, while limiting the self-configuration rights of independent node operators, has sparked the 'OP_RETURN war' among Bitcoin maintainers. The debate has lasted through the weekend and is expected to continue this week across platforms like GitHub, Bitcoin-Dev Google Group, StackerNews, Reddit, BitcoinTalk, X, and many others.
Impact on the Crypto Market
This event brings many signals:
Technology Development: Raising the OP_RETURN limit could expand the capacity for storing non-financial data, supporting projects like Tether AI (open-source integrated Bitcoin-USDT) and BitcoinOS (converting $BTC to Cardano).
Consensus Risks: Lack of consensus could cause a rift in the community, affecting Bitcoin's price and market confidence.
Enhanced Security: The controversy highlights the need for transparency, especially after bridge hack incidents like Nomad ($190 million).
Conclusion: How Will OP_RETURN Change Bitcoin?
The OP_RETURN war erupted when a group of developers attempted to raise the data limit via PR 32359, arguing for 'reducing harm' to Bitcoin, particularly concerning Citrea. Although halted due to concerns about censorship and business interests, this controversy opens discussions about the future of data storage on the blockchain. Investors should closely monitor to assess the impact on technology and the crypto market.
Risk Warning: Crypto investment carries high risks due to price volatility and legal uncertainties. Please consider carefully before participating.