Jessy, Golden Finance
On June 9, Bitcoin core developers plan to release version 30 of Bitcoin Core software in October this year, which will no longer filter OP_RETURN outputs containing a large amount of non-financial data. This change will increase the default data carrier limit from the current 80 bytes to nearly 4MB, while allowing node operators to manually modify the -datacarrier and -datacarriersize parameters.
As soon as the news came out, it immediately triggered a heated discussion within the Bitcoin community. Proposal supporters believed that this was a necessary step to unleash the potential for innovation on the chain, while opponents saw it as a betrayal of the core values of Bitcoin. The intensity of the emotions even caused some Bitcoin holders to liquidate and leave.
The OP_RETURN expansion storm has lasted for nearly two years. Although the core developers plan to implement the expansion in the Bitcoin Core software updated in October, the controversy continues, and this is not the final result.
What is expansion? Why is there controversy?
The storm started as early as July 2023.
On July 23, 2023, Peter Todd, a core developer and core promoter of the expansion faction, submitted PR#28130, proposing to remove the restriction on OP_RETURN carrying data, but failed.
OP_RETURN is an opcode in Bitcoin script that is used to embed small amounts of data in Bitcoin transactions. It allows users to store data on the blockchain, but these outputs are "provably unspendable" and therefore do not increase the burden on the UTXO (unspent transaction output) set. The current default limit of Bitcoin Core is that the OP_RETURN data size is 80 bytes, and the propagation of OP_RETURN transactions larger than 83 bytes is restricted by node policy (not consensus rules).
On April 28, 2025, Peter Todd submitted the same proposal PR#32359 again, and instagibbs proposed a relatively mild proposal PR#32406, suggesting that the configuration option be retained temporarily, but without restrictions by default. On June 9, Bitcoin Core developer Gloria Zhao posted on GitHub that the Bitcoin Core 30 update, scheduled for October 30, will remove the 80-byte limit on the OP_RETURN function, allowing each output to carry up to 4 megabytes of data. At present, the controversy caused by the change is still ongoing, and there are major differences in the community's views on this change.
The core claim of these developers who promote expansion is roughly that the current 80-byte limit hinders the development of key applications. For example, data embedding that complies with the W3C verifiable credential standard requires more than 96 bytes of space, and enhanced lightning network atomic swap metadata and complex state proofs of the RGB protocol may also be affected by the 80-byte limit, resulting in the inability to fully or efficiently implement related functions.
As soon as this news came out, it once again triggered a heated debate in the Bitcoin community, with the pros and cons holding their own opinions, and opponents also expressing their protests with actions. For example, on June 11, Jason Hughes, vice president of the mining pool OCEAN, announced that he would sell all his bitcoins and withdraw from the industry to protest the recent OP_RETURN change decision.
This expansion dispute, which has been spreading for nearly two years, triggers a lot of discussion every time there is a new development, but more discussions are about the disagreements within the Bitcoin Core development team and the resulting debates among extreme believers in Bitcoin. For example, some developers believe that a small expansion has controllable risks and obvious benefits; the other faction strongly opposes it, fearing that it will slide into the abyss of functional expansion. Technical discussions quickly escalated into a battle of ideas.
Interestingly, mainstream mining pools and exchanges generally do not express their views on this.
The core of the dispute: What is the ultimate role of Bitcoin?
Supporters first start from the original design of Satoshi Nakamoto. They believe that the Bitcoin protocol in the Satoshi era did not have any data size restrictions on OP_RETURN. Removing the 80-byte limit is a return to the original spirit of Bitcoin, which is in line with its nature as an open system. Technology should remain open and its use is determined by community innovation. The current 80-byte limit can be bypassed by directly submitting to the miner mempool (such as MARA Slipstream) or unrestricted nodes (such as Libre Relay), which is tantamount to ineffectiveness, so removing the limit will not actually bring more risks.
On the other hand, capacity expansion will also reduce the burden on the network. For example, protocols such as inscriptions currently use multiple transactions to store data exceeding 80 bytes. After removing the restrictions, inscriptions can directly store data through OP_RETURN, reducing unnecessary multiple transactions, thereby reducing the pressure on the network.
In addition, after capacity expansion, miners' income can be increased. With the halving of Bitcoin every four years, miners' income has decreased. Allowing large-size OP_RETURN transactions can allow miners to earn more income by competing for block space, motivating miners to continue to invest in computing power and consolidate the security of the Bitcoin network.
The main point of opponents is that this move will squeeze block space. Removing restrictions may cause more non-transaction data (such as spam, low-value tokens, etc.) to be written to the chain, squeezing block space, and then pushing up transaction fees, affecting the efficiency and practicality of Bitcoin as a value transfer network. And this goes against the original design of Bitcoin as a value transfer network, and may reduce the blockchain to a data storage platform, keeping images, text, and audio away from the blockchain, and maintaining the "purity" of Bitcoin for accounting rather than data storage.
In addition, the removal of configuration options from Bitcoin Core (such as -datacarrier and -datacarriersize) is considered to deprive users of the right to choose independently and force the adoption of a "paternalistic" strategy, while retaining configuration options is more in line with Satoshi Nakamoto's decentralized concept of "one CPU one vote".
The controversy is so intense, and what everyone is essentially discussing is what is the ultimate role of Bitcoin in this world? Is it pure, unalterable "digital gold" and the cornerstone of value storage? Or is it an underlying settlement layer that supports limited but useful applications?
OP_RETURN expansion touches on this fundamental philosophical disagreement. Opponents believe that any attempt at application is a blasphemy against "sacredness"; supporters believe that only moderate evolution can be endless. Times are changing, new public chains are constantly emerging, and Bitcoin is once again at the crossroads of choice.
Hui Xin
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