Wiki / Events / The 2025 OP_RETURN fight

The 2025 OP_RETURN fight

From the Bitcoin Takeover Wiki · ✓ 6 sources · 2 podcast anchors · built 2026-11-13

The 2025 dispute over Bitcoin Core lifting its default OP_RETURN limit, which pushed opponents to Bitcoin Knots and fed the BIP-110 fork effort.

◆ Takeover vieweditorial · opinion, labelled

The wiki's angle: the first major fork fight since 2017 to be about what goes in blocks, not how big they are, and it put Bitcoin Knots in the role Bitcoin Classic and Unlimited once played.[4][3]

Contents

  1. Change
  2. Core's statement
  3. Opposition
  4. References

Change

Bitcoin Core PR #32406, “policy: uncap datacarrier by default”, was opened by instagibbs on 2 May 2025 and merged on 9 June 2025[1]. The Bitcoin Core 30.0 release notes say that -datacarriersize “is increased to 100,000 by default, which effectively uncaps the limit”, that it can be overridden with -datacarriersize=83 to revert, and that multiple OP_RETURN outputs are now permitted[2].

Core's statement

On 6 June 2025 Bitcoin Core published “Bitcoin Core development and transaction relay policy”, which said: “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”[3].

Opposition

The Takeover BLAKE2b feature says that since the Ordinals wave of 2023 a vocal part of the community has seen inscriptions and large OP_RETURN outputs as spam, that Core “went the other way” in 2025, and that Bitcoin Knots “became the home of the opposition”[4]. Charlie Spears said on the show that the modern debate kicked off from a mailing-list issue after a Citrea presentation at OP_NEXT[5]. Bob Summerwill argued that data carrying could be disliked without being banned by consensus[6]. See Ordinals and Bitcoin BLAKE2b[4].

References

  1. primaryBitcoin Core PR #32406, “policy: uncap datacarrier by default” (instagibbs; opened 2 May 2025, merged 9 Jun 2025) [archived]
  2. primaryBitcoin Core 30.0 release notes (datacarriersize default 100,000; multiple OP_RETURN outputs) [archived]
  3. primaryBitcoin Core, “Bitcoin Core development and transaction relay policy” (6 Jun 2025) [archived]
  4. btkBitcoin BLAKE2b: The Fork That Fired the Miners (BTCTKVR: Forks!) [archived]
  5. episodeS17 E13: Charlie Spears on OP_NEXT and the OP_RETURN debate▶ listen at 1:23:04timestamp transcript-derived, pending a listen [archived]
  6. episodeS17 E42: Bob Summerwill on BIP-110 and data-carrying▶ listen at 1:03:10timestamp transcript-derived, pending a listen [archived]

Related

Bitcoin Knots
Luke Dashjr's derivative of Bitcoin Core: the long-running alternative client that became the base of the 2025
Ordinals and inscriptions
Casey Rodarmor's numbering scheme for satoshis and the inscriptions built on it, which put arbitrary data in T
Luke Dashjr
Bitcoin Knots maintainer; central figure of BIP-110 and the 2026 BLAKE2b fork.
Bitcoin BLAKE2b (XBT / BTCB2)
The 2026 fork that grew out of Luke Dashjr's BIP-110 anti-spam soft fork and replaced SHA-256d with BLAKE2b. S
Kurt Wuckert Jr.
Self-described Bitcoin historian on the BSV side, CoinGeek author and GorillaPool operator, interviewed on Bit
Categories: Events
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