Bitcoin Core Merges the Contested OP_RETURN Relay-Policy Change
Bitcoin Core merged a relay-policy change that effectively removed the old 83-byte default OP_RETURN limit and allowed multiple data-carrier outputs per transaction. The change was not a consensus rule, but it became a concrete implementation stage in the broader 2025 OP_RETURN governance dispute.
On June 9, 2025, Bitcoin Core merged pull request #32406, turning a heated policy debate into a concrete implementation change. The patch raised the default -datacarriersize setting from 83 bytes to 100,000 bytes, effectively removing the old OP_RETURN size limit as a practical relay constraint because transactions would encounter other size limits first. It also allowed multiple OP_RETURN outputs in a transaction and applied the configured data-carrier limit across their combined script size.
The change concerned node relay and mining policy, not Bitcoin consensus. Nodes running other software or custom settings remained free to reject or filter transactions differently, and blocks containing transactions outside a node’s local relay policy could still be valid under consensus rules. That distinction was central to the dispute: supporters argued that users were already finding other ways to place arbitrary data in transactions and that the old default encouraged less transparent workarounds, while opponents argued that removing the limit weakened anti-spam norms and changed the role Bitcoin Core should play in transaction policy.
The merge became an important middle stage in a governance controversy that had broken into the open in May. It did not end the argument. The policy later shipped in Bitcoin Core 30.0 and helped fuel a wider Core-versus-Knots dispute over defaults, filtering and developer influence. June 9 therefore marked the point at which the disputed policy moved from proposal and debate into the main Bitcoin Core codebase.