Bitcoin Core v30's Expanded Data Limit Draws Criticism, Labeled 'Tax' on Nodes

Bitcoin Core version 30 (v30), released in October 2025, has ignited significant debate within the cryptocurrency community due to its controversial expansion of the OP_RETURN data limit. This update, which introduces several node-related changes, has been met with both support and strong criticism from prominent figures. Justin Bechler, a notable voice in the Bitcoin space, starkly characterized the update, stating, > "Make no mistake, at its most fundamental, Core 30 is a tax on all Bitcoin nodes."

The primary feature sparking contention is the increase in the default OP_RETURN data limit from 80 bytes to 100,000 bytes, effectively allowing up to nearly 4MB of non-financial data per transaction output, constrained only by overall transaction size limits. This policy modification enables significantly larger amounts of arbitrary data to be embedded within Bitcoin transactions. Bitcoin Core developers assert this change aims to align default node policies with how miners already process large data payloads.

Critics argue that this expansion could lead to blockchain bloat, increased operational costs for node runners, and potential legal liabilities for storing arbitrary, potentially illicit content. Luke Dashjr, lead developer of the alternative Bitcoin Knots client, has been a vocal opponent, warning that node operators might unwittingly become complicit in storing and spreading illegal material. Cryptographer Nick Szabo also advised against upgrading to Core v30, suggesting users "run Knots" as a temporary measure.

Conversely, proponents of Core v30 emphasize network neutrality and the potential for new applications. Gloria Zhao, a Bitcoin Core maintainer, argues the change aligns the software with existing mining practices and that OP_RETURN data is "prunable and less harmful" than other on-chain data storage methods. Alex Bergeron of Ark Labs expressed intentions to utilize the expanded OP_RETURN space for developing new Bitcoin applications, with Jameson Lopp and Pavol Rusnak also voicing support for the update.

The divergence in opinion has led to a notable shift in the node landscape, with Bitcoin Knots seeing increased adoption as some operators seek to maintain stricter data limits. While Core v30 does not alter Bitcoin's consensus rules, its implications for the network's identity—whether it remains solely a monetary layer or accommodates broader data use—are profound. Node operators are now faced with the decision to adopt the new Core v30, switch to alternatives, or delay upgrades, as versions 27.x and older have reached their end-of-life.