TL;DR: The standardness restrict on OP_RETURN outputs was lifted by default as a result of it did extra hurt than good.
Disclaimer: I’m the creator of the proposal to raise this coverage restrict.
The OP_RETURN coverage restrict was launched as a nudge to fee restrict the quantity of arbitrary knowledge printed onchain. By tolerating some small quantity of arbitrary knowledge publication (as much as 80 bytes) via the general public relay community, it might incentivize builders of purposes wishing to publish arbitrary knowledge to adapt their software program to those limits moderately than constructing other ways to succeed in miners.
This restrict grew to become out of date when customers began exploiting the witness low cost to retailer arbitrary knowledge in transaction witnesses. This technique is named “inscriptions” and permits to retailer near 400kb of information (i.e. 5000x extra knowledge than customary OP_RETURN outputs). These “inscriptions” created a pattern and shortly grew to become the principle driver of block area demand, producing tons of of thousands and thousands of {dollars} in mining charges.
In the meantime, infrastructure was being constructed to make it simpler to bypass the general public relay community and subsequently Bitcoin Core’s relay coverage. APIs to submit transactions on to miners, various peer-to-peer networks with looser relay coverage restrictions, and a broad curiosity from customers and builders to construct these options. Subsequently whereas the OP_RETURN restrict particularly was made out of date by inscriptions, nudging with paternalistic coverage limits typically was made much less efficient as an software builders now has entry to many options to entry the block chain.
A superb instance of this dynamic is the latest “sub 1sat/vb summer season” pattern. Bitcoin Core has for a decade solely ever relayed transactions paying a feerate of at the least 1sat/vb. This was one of the well-known and accepted relay coverage restrict. Throughout the summer season of 2025 a lot of customers, builders and miners “memed” themselves into bypassing this restrict. In a short time, near half of all transactions included within the block chain had been transactions that no model of Bitcoin Core would relay by default. This simply goes to point out how fragile coverage limits actually are, and that they’re unsuitable to counteract what will get included within the block chain.
Whereas the OP_RETURN coverage restrict was obsoleted by inscriptions, and whereas relay coverage limits are in any case unsuitable for counteracting how block area will get used, they did do one thing. By definition, the OP_RETURN restrict prevents leveraging the peer-to-peer transaction relay community. Utilizing this community, whereas not essential to get entry to dam area, nonetheless has worth. It’s to at the present time the easiest way to make sure quick and strong propagation to nearly all of miners. That is a vital property for second-layer protocols (just like the Lightning Community), whose safety depends on having the ability to get a transaction confirmed in a well timed method.
If it was the case that some software wished to retailer arbitrary knowledge in non-witness elements of a Bitcoin transaction whereas nonetheless benefiting from the properties of the peer-to-peer transaction relay community, the OP_RETURN coverage restrict would truly be counterproductive! It will create an incentive for such customers to masquerade the information they wish to publish as actual, spendable, transaction outputs. This fashion they’ll nonetheless publish the information in non-witness elements of the transactions AND they’ll nonetheless profit from the properties peer-to-peer transaction relay community. A relay coverage that creates perverse incentives is horrible: that is the polar reverse to what it’s imagined to be doing! The OP_RETURN coverage restrict was not serving its supposed function anymore, but it was created perverse incentives. From a principled standpoint, it needed to be lifted.
It’s the case that some software wished to retailer arbitrary knowledge in non-witness elements of a Bitcoin transaction whereas nonetheless benefiting from the properties of the peer-to-peer transaction relay community. The Citrea bridge is an instance of that. And guess what, they began masquerading the information they needed to publish as spendable outputs! This offered additional proof that the OP_RETURN coverage restrict was now a legal responsibility and was the set off for my proposal.
The OP_RETURN coverage restrict did extra hurt than good and that’s the reason it was proposed to be lifted, and the proposal accepted.
Doesn’t uncapping by default improve the bandwidth and storage burden on each full node?
No. The storage burden is bounded by the consensus restrict on the block measurement. The bandwidth burden on a node relies on utilization patterns on the community. For example if it was widespread to make use of OP_RETURN outputs bigger than 80 bytes and also you saved this coverage restrict by yourself node (with the -datacarriersize choice in Bitcoin Core), it might presumably improve the bandwidth burden of your node. Subsequently lifting the restrict on this case would scale back your bandwidth burden. However i do not suppose this may occur, and i feel bandwidth utilization will likely be unaffected.
Doesn’t uncapping by default create potential authorized dangers for operators compelled to retailer arbitrary or illicit knowledge.
No. There could also be danger related to a Bitcoin node, since you can not forestall the storage of arbitrary knowledge. These dangers are usually not materially affected by this alteration, if solely as a result of for something that may be saved in a 100KB OP_RETURN output, one thing 4x greater (and subsequently probably extra dangerous) can already be saved in a 400KB inscription. It will use a unique encoding, however this has no bearing on the legality of the saved content material. It is also the case that somebody malicious prepared to retailer nefarious content material in a big OP_RETURN particularly (for some purpose) can already achieve this at this time at minimal value. Once more, relay coverage are usually not appropriate to counteract how block area will get used.
Would not danger mission drift by encouraging non-monetary use of Bitcoin’s scarce block area?
This transformation doesn’t encourage non-monetary use of Bitcoin. Customers wishing to make use of Bitcoin to retailer arbitrary knowledge can already use inscriptions which might be 4x cheaper to make use of for a similar quantity of information, and in addition permit to retailer as much as 4x the quantity of information.
For extra concerning the implication of this alteration, please see this reply.
