Bitcoin Core Removes OP_RETURN Output Limit

A unilateral decision by Bitcoin Core will scrap the controversial OP-Return limit.

The proposal to remove the 80-byte limit on OP_RETURN outputs was accepted and will feature in the next release of the most widely used node software.

With the change, the limit on adding arbitrary data to Bitcoin transactions will no longer apply.

“Bitcoin Core’s next release will, by default, relay and mine transactions whose OP_RETURN outputs exceed 80 bytes and allow any number of these outputs,” announced Bitcoin developer Greg Sanders on GitHub on May 5.

The long-standing limit was originally a “gentle signal that block space should be used sparingly for non-payment proof of publication data, but it has outlived its utility,” he stated.

The change, which was requested by Chaincode Labs and had contributions from Peter Todd, an early Bitcoin innovator, is covered by pull request no. 32359.

What Is OP_RETURN?

OP_RETURN is a script opcode that people can use to write arbitrary data on the blockchain and also mark a transaction output as invalid.

Unlike typical transaction outputs, OP_RETURN outputs cannot be used for spending and don't impact the number of unspent transaction outputs (UTXOs).

According to Sanders, the initial limit no longer serves its purpose, with people exploiting methods like fake output addresses that worsen the network and some mining services disregarding the restriction.

“Inscriptions of large data are happening regardless and can be done in more or less abusive ways; the cap merely channels them into more opaque forms that cause damage to the network.”

Removing the limit, he argued, “yields at least two tangible benefits: a cleaner UTXO set and more consistent default behavior.”

Three options were evaluated: keeping the cap, raising it, or removing it. They decided to eliminate the cap, which garnered “broad, though perhaps not unanimous, support.”

“Many users find this to be an undesirable change for a number of reasons,” said Bitcoiner Samson Mow on X on May 5.

Adding that users “can refuse to upgrade and stay on 29.0 or run another implementation” of the network.

This Point of View: Bitcoin Devs' Unilateral Decision Sparks Outrage

Critics argued that the proposal lacked proper consensus and DEVI expressed concerns about Bitcoin's financial utility being downshifted. They also pointed out the possibility of undisclosed conflicts of interest.

“I think one thing is pretty clear, there is no moment on this issue at the moment. DEVI