Bitcoin Core Update to Remove Data Limit for OP_RETURN

Bitcoin Core developers will remove the default data limit for OP_RETURN in the client release v30, scheduled for October.

I posted a full writeup for the #32406 merge decision on the PR.

These changes go into effect in v30, which is scheduled for release in October.
The PR changes the defalt value of -datacarriersize. You will still be able to use -datacarrier and -datacarriersize options in v30,…

— gloria (@glozow) June 9, 2025

The effective limit will be the 4 MB block size. Users can still manually set a limit by specifying the -datacarriersize argument, which will remain available but marked as deprecated.

Debates over the data size in OP_RETURN intensified since late April. Bitcoin developer Peter Todd, who was dubbed the creator of the first cryptocurrency in an HBO documentary, proposed removing the existing 83-byte limit.

The initiative divided the community. Opponents argue that lifting the restriction encourages the use of the network for non-financial transactions, potentially overloading the blockchain.

Critics point out that users still find alternative ways, and miners have the opportunity and incentives to include such operations in a block.

In May, developers prepared code changes intended to be included in the next client release.

In early June, the Bitcoin Core team penned an open letter explaining their decision to remove the OP_RETURN limit. They stated that any restrictions ultimately contradict the fundamental principles of the first cryptocurrency—decentralization and censorship resistance.

“This does not mean approval or encouragement of using non-financial data, but rather an acknowledgment that a censorship-resistant system can and will be used even in cases not everyone agrees with,” the letter’s authors stated.

Some Bitcoin supporters reacted sharply to the developers’ decision to remove the OP_RETURN limit. Co-founder and CEO of Satoshi Action Fund, Dennis Porter, noted that he had helped raise $200,000 for the Bitcoin Core team.

I’ve helped raise over $200,000 for core devs during my time in Bitcoin. My faith in their work is now broken.

I will no longer be financially supporting Core Development.

I have begun exploring other implementations to support.

Dm me if you are interested in joining me.

— Dennis Porter (@Dennis_Porter_) June 10, 2025

“My faith in their work is now broken. I will no longer be financially supporting and have begun exploring other implementations,” he wrote.

The vice president of the Ocean mining pool stated that developers made a corporate-style decision, disregarding user positions. In his view, this undermines Bitcoin as the benchmark monetary system and threatens the network’s future.

52 days.

That’s all it took for a non-Bitcoin project to co-opt Bitcoin Core’s development and direction.

If that doesn’t terrify you, it should. If such an insignificant shitcoin entity can shift Bitcoin Core’s development so easily with so little influence, despite massive…

— Jason Hughes (@wk057) June 9, 2025

“Personally, I have no strength for this fight. Users must stand against this nonsense and not let Bitcoin Core kill Bitcoin,” he emphasized.

Prominent Bitcoin advocate Jimmy Song also noted that removing the OP_RETURN data limit will lead to more “junk” in the network.

According to video blogger Matthew Kratter, the developers’ decision could spell trouble for Bitcoin Core. Ignoring community opinion has already led to a loss of market share, and within one to three years, it could shrink from the current 88% to 20-30%, the expert believes.

In 1-3 years from now, expect Bitcoin Core’s market share to have fallen to 20-30% https://t.co/bxarqFDcjj

— Matthew R. Kratter (@mattkratter) June 9, 2025

In June, on-chain activity in the first cryptocurrency’s network dropped to levels seen in October 2023.