The controversy surrounding Bitcoin's OP_RETURN has intensified, as developers of Bitcoin Core, the most widely used node software, have announced plans to remove the OP_RETURN limit entirely in the next release. The OP_RETURN limit is a restriction of 80 bytes on the amount of arbitrary data that can be embedded in a Bitcoin transaction using a special, unspendable output field. According to Core contributor and Blockstream Engineer Greg Sanders, "Large-data inscriptions 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." The debate centers around whether removing the 80-byte OP_RETURN limit will promote transparency and simplify data use on Bitcoin, or if it will lead to abuse, spam, and a shift away from Bitcoin's financial focus. On Github, Sanders noted that enforcing the cap has created incentives for users to embed data in fake public keys or spendable scripts, and argued that removing the limit will result in "a cleaner UTXO set and more consistent default behavior." However, not everyone agrees with this decision.
Core developer Luke Dashjr has long considered inscriptions and other data storage as spam and warned in April 2025 that this change was "utter insanity." Amid the controversy, Bitcoin Knots, maintained by Dashjr, has seen growing adoption, reaching approximately 5% of all nodes. Bitcoin Knots, a customizable fork of Bitcoin Core, appeals to users seeking greater control over what their nodes relay or store, including the ability to reject non-payment transactions like inscriptions.
Some prominent industry thought leaders, such as Samson Mow, are advising node operators not to upgrade their version of Bitcoin Core or to use Knots instead. Sanders defended the removal of the cap, stating that it aligns with Bitcoin's ethos of minimal, transparent rules. "By retiring a deterrent that no longer deters," he wrote, "Bitcoin Core lets the fee market arbitrate competing demands." However, this decision has not brought about much consensus.
"This marks a fundamental shift in the direction of Bitcoin," one commenter warned on GitHub. "This is the largest mistake Core can make at this juncture," another added on Github.