Bitcoin’s OP_RETURN Limit Soars to Nearly 4MB in Core 30 Update

The Bitcoin Core development team has announced a major update in the upcoming October Core 30 release.

The changes will increase the OP_RETURN data limit from 80 bytes to nearly 4 MB.

Community Debate

The proposal removes the long-standing default size limits on OP_RETURN, a transaction commonly used to embed non-financial data into the blockchain. Right now, Bitcoin Core only allows a small amount of data in OP_RETURN. The update would let Core relay much larger transactions by default.

The idea has received both support and criticism on GitHub, with the debate centered on whether Bitcoin nodes should block non-monetary transactions or act as neutral relayers of any valid transaction.

Those against it argue that removing the limit could invite spam and non-monetary data into Bitcoin blocks, which could occupy space intended for financial transactions. According to them, keeping the current limits protects Bitcoin’s economic value and keeps it efficient. They also say that removing settings like -datacarriersize would reduce node control.

Comments from Seccour, chrisguida, and wizkid057 express concern that the change gives in to spammers and encourages misuse of Bitcoin. They all agree that the network should resist spam instead of making it easier.

Supporters of the update believe that storing arbitrary data on Bitcoin is already happening and cannot be stopped. They say trying to block it leads to users resorting to worse methods, such as making private deals with miners.

The group argues that OP_RETURN is the least harmful method. This is because it is small, cannot be spent, and does not add to the UTXO set. They say increasing the limit can guide data use to this cleaner method and avoid worse alternatives.

Comments from murchandamus and eragmus support the decision, with one arguing that it would reduce node traffic and help prevent miner centralization. The other explained that it is a practical change that matches how the network is already used.

A Push for Greater Decentralization

Bitcoin Core has limited OP_RETURN to 80 bytes since 2014. However, developers announced in May that the cap would be removed in the next version. In a recent statement, they explained that the decision aligns with Core’s goal of reflecting economically relevant activity by ensuring that transactions likely to be mined are relayed.

They added that blocking these transactions weakens decentralization, drives users to alternative channels, and ultimately fails to keep the data off the blockchain. Allowing them, they explained, preserves Bitcoin’s censorship resistance and ensures the network operates efficiently.

“This is not endorsing or condoning non-financial data usage, but accepting that as a censorship-resistant system, Bitcoin can and will be used for use cases not everyone agrees on,” the statement read.

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