# A Comprehensive OP\_RETURN Limits Q&A Resource to Combat Misinformation **URL:** \ **Category:** Philosophy\ **Tags:** mempool, bitcoin-core\ **Created:** [May 12, 2025, 5:30pm UTC](https://delvingbitcoin.org/t/a-comprehensive-op-return-limits-q-a-resource-to-combat-misinformation/1689 "2025-05-12T17:30:05Z")\ **Posts on this page:** 4\ **Page:** 1
**Author:** ![tidwell](https://delvingbitcoin.org/letter_avatar_proxy/v4/letter/t/ec9cab/32.png) [@tidwell](https://delvingbitcoin.org/u/tidwell)\ **Post date:** [May 12, 2025, 5:30pm UTC](https://delvingbitcoin.org/t/a-comprehensive-op-return-limits-q-a-resource-to-combat-misinformation/1689/1 "2025-05-12T17:30:05Z")
My goal is to share a consolidated list of questions about OP\_RETURN limits that we’ve answered on Stacker News, as the original thread has become unwieldy with over 200 comments. We began compiling this list about a week ago. I’ve frequently shared individual links and received very positive feedback. I hope this resource helps us work from a common set of facts and reduces misinformation. I hope you find this as a valuable resource. Special thanks to @murch for encouraging me to ask questions and for taking the time to field many of them. I’ll list the questions in order of activity and tips received. I’ve removed duplicates, rephrased some statements as questions, and ignored completely irrelevant questions. 1. Users should be given clear configurable options to decide what’s in their mempool, why were these options taken away? [link](https://stacker.news/items/971277/r/tidwell?commentId=971285) 2. Won’t spammers abuse large OP\_RETURNs to bloat the blockchain and make IBD take longer? [link](https://stacker.news/items/971277/r/tidwell?commentId=971284) 3. A similar PR was proposed by Peter Todd 2 years ago, why was it rejected then? What has changed since then, why would this get approved now? [link](https://stacker.news/items/971277/r/tidwell?commentId=971297) 4. Shouldn’t we be fighting spam, why are we making policies less strict, shouldn’t we be making them more strict? [link](https://stacker.news/items/971277/r/tidwell?commentId=971287) 5. How would someone get around the standardness policy currently for OP\_RETURN size? [link](https://stacker.news/items/971277/r/tidwell?commentId=971281) 6. What does “standardness mean” in reference to OP\_RETURNs? [link](https://stacker.news/items/971277/r/tidwell?commentId=971280) 7. Will more than 1 OP\_RETURN per transaction be possible if this PR gets merged? [link](https://stacker.news/items/971277/r/tidwell?commentId=971280) 8. What are the current OP\_RETURN limits and what restrictions are being lifted? [link](https://stacker.news/items/971277/r/tidwell?commentId=971278) 9. Are current relay and mempool policies effective for filtering out spam transactions? [link](https://stacker.news/items/971277/r/tidwell?commentId=971288) 10. Is it true that this type of update could affect Bitcoin’s decentralization? [link](https://stacker.news/items/971277/r/tidwell?commentId=971934) 11. Is it possible to stop the abuse of payment outputs (i.e., bare multisig, fake pubkeys, and fake pubkey hashes) that are used to embed data, thereby creating unprunable UTXOs that bloat the UTXO set? [link](https://stacker.news/items/971277/r/tidwell?commentId=971325) 12. What was the main reason /concern to add this PR? … What will happen if we do nothing? [link](https://stacker.news/items/971277/r/tidwell?commentId=971824) 13. If OP\_RETURN still cannot stop all the garbage, why is so important to remove it? Does it affect future development / improvements for LN? [link](https://stacker.news/items/971277/r/tidwell?commentId=971309) 14. What will be the worst case scenario if users still could set their own limits for OP\_RETURN? [link](https://stacker.news/items/971277/r/tidwell?commentId=971311) 15. Shouldn’t we debate the controversy of this PR on Github since it’s where the code gets merged to make these changes? [link](https://stacker.news/items/971277/r/tidwell?commentId=971330) 16. What does it mean when someone says “Fix the Filters”? [link](https://stacker.news/items/971277/r/tidwell?commentId=971289) 17. Will this open the flood gates and drown out all legitimate onchain activity? [link](https://stacker.news/items/971277/r/tidwell?commentId=971391) 18. What can we do to stop spam at the consensus layer of Bitcoin? [link](https://stacker.news/items/971277/r/tidwell?commentId=971326) 19. Will Taproot wizards and other spam companies and projects start using OP\_RETURN to put jpegs on the blockchain? [link](https://stacker.news/items/971277/r/tidwell?commentId=971293) 20. If we prevent these transaction from going into our mempools doesn’t that prevent or delay these spam transactions from being mined therefore discouraging the spammers? [link](https://stacker.news/items/971277/r/tidwell?commentId=971291) 21. Is it possible to stop abuse of witness data? If so, how? (i.e ordinal theory inscriptions, “jpegs”). [link](https://stacker.news/items/971277/r/tidwell?commentId=971321) 22. Is there any conflict of interest with Bitcoin Core and companies like Citrea, in ref to this PR? [link](https://stacker.news/items/971277/r/tidwell?commentId=971302) 23. Is there any estimation on how much would this affect fees for the average user, considering external projects (like Citrea) using it? Any possibility that this could saturate the mempool and boost fees beyond reasonable? [link](https://stacker.news/items/971277/r/tidwell?commentId=971403) 24. Was this PR initially proposed because of Citrea BitVM needs? If so don’t they only need a slight bump in OP\_RETURN size, why is it being proposed to make the size unrestricted? [link](https://stacker.news/items/971277/r/tidwell?commentId=971300) 25. What makes a UTXO unprunable? Which projects are making unprunable UTXOs? [link](https://stacker.news/items/971277/r/tidwell?commentId=971296) 26. Why would a spammer use OP\_RETURN if it’s cheaper to use Witness data to store arbitrary data? [link](https://stacker.news/items/971277/r/tidwell?commentId=971294) 27. Won’t large OP\_RETURNs allow people to spam the mempool with 100kb transactions and mess up bitcoin for everyone by bloating the mempool and not allowing legitimate transactions in the mempool? [link](https://stacker.news/items/971277/r/tidwell?commentId=971292) 28. If relaxing op\_return standardness limit seeks to make ‘spam’ prunable, then what are proponents of this change assuming about the long-term feasibility of running a ‘full’ (unpruned) bitcoin node? [link](https://stacker.news/items/971277/r/tidwell?commentId=971592) 29. Is allowing standardness for larger OP\_RETURNs a slippery slope? If we allow this won’t we continue to allow things that make bitcoin less for money and more for arbitrary data? [link](https://stacker.news/items/971277/r/tidwell?commentId=971299) 30. Won’t removing the OP\_RETURN cap reduce fee market pressure by allowing senders to consolidate arbitrary data into a single transaction? [link](https://stacker.news/items/971277/r/tidwell?commentId=972132) 31. Could this PR be the beginning of reducing other mempool restrictions? [link](https://stacker.news/items/971277/r/tidwell?commentId=971912) 32. Culture is what protects Bitcoin from external forces, shouldn’t non-technical arguments be valid when considering these types of changes? [link](https://stacker.news/items/971277/r/tidwell?commentId=971331) 33. What’s the difference between UTXO set, mempool, and blockchain, and how do larger OP\_RETURN or witness data affect node resource usage? [link](https://stacker.news/items/971277/r/tidwell?commentId=971314) 34. What is the difference in defining a transaction as valid versus defining a transaction as standard and why do we need this difference? [link](https://stacker.news/items/971277/r/tidwell?commentId=971308) 35. If you’re happy with your viewpoint on consensus and mempool rules, is not upgrading Bitcoin Core until it makes sense to you a valid action to take right now? [link](https://stacker.news/items/971277/r/tidwell?commentId=972071) 36. Why didn’t this PR get a BIP number? [link](https://stacker.news/items/971277/r/tidwell?commentId=973745) 37. Why is core rushing this change? [link](https://stacker.news/items/971277/r/tidwell?commentId=973744) 38. If there will be a hard fork resulted from this PR (split chain like in 2017), what will happen with existing LN channels? Will exist on both chains with 2 LNs? [link](https://stacker.news/items/971277/r/tidwell?commentId=971840) 39. Isn’t this all moot in a (almost guaranteed) future where fees are very high? [link](https://stacker.news/items/971277/r/tidwell?commentId=977652) 40. What is this controversy about, and what is it _really_ about? [link](https://stacker.news/items/971277/r/tidwell?commentId=974539) ---
**Author:** ![FernandoTheKoala](https://delvingbitcoin.org/letter_avatar_proxy/v4/letter/f/71c47a/32.png) [@FernandoTheKoala](https://delvingbitcoin.org/u/FernandoTheKoala)\ **Post date:** [September 8, 2025, 1:18pm UTC](https://delvingbitcoin.org/t/a-comprehensive-op-return-limits-q-a-resource-to-combat-misinformation/1689/2 "2025-09-08T13:18:43Z")
First of all thank you for your guide, very useful. In regard to point#24, specifically as to why the limit has been increased so much to 100’000 bytes, the given motivation is: _“…undemanded blockspace is no longer a thing. OP\_RETURN outputs would have to compete for blockspace with other transactions at all times. The limit is neither as important nor as effective today as when it was introduced. Instead of providing mining pools with a financial incentive to accept oversized OP\_RETURN outputs out of band, and to have debates to slightly loosen the limit further every once in a while, it seems easier to get rid of the incentive and debates by dropping it altogether_”. The given motivation claims that the limit is irrelevant as large op\_return will be pushed out by market forces. In regard to the latest claims that in this way (with 100’000 bytes for op\_return) CP images can: 1. be uploaded as a single jpeg which is visible/clear enough 2. It is possible to visualize it in a much much simpler way (being a single hash) compared as to other data already embedded in the blockchain but that are “fractured” in multiple txs and are much harder to reconstruct? If the 2 points above are correct, would not this expose btc to a massive risk of having CP images uploaded on the chain? (I’m referring to legal risks here). If this is the case a sufficiently motivated actor will not be discouraged by large fees, also as it would be enough to upload 1 of these images to have enough reasons/proofs to his advantage. Since this specific case has surfaced aggressively in the recent discussions, and there seems to be contradicting ideas (on how easy it is to visualize it) i would be appreciated to have some clarification on this ---
**Author:** ![garlonicon](https://delvingbitcoin.org/letter_avatar_proxy/v4/letter/g/278dde/32.png) [@garlonicon](https://delvingbitcoin.org/u/garlonicon)\ **Post date:** [September 9, 2025, 6:28am UTC](https://delvingbitcoin.org/t/a-comprehensive-op-return-limits-q-a-resource-to-combat-misinformation/1689/3 "2025-09-09T06:28:54Z")
> If the 2 points above are correct, would not this expose btc to a massive risk of having CP images uploaded on the chain? There are much worse ways to push data on-chain, than OP\_RETURN. For example, it is possible to use some future Segwit version, and push everything, as a continuous 4 MB witness data chunk. Also, 520-byte chunks can be easily collected, and displayed, so even if some data will be fragmented between many outputs, many transactions, and many coins, then it doesn’t matter, because writing a parser, which will collect all of that, and display it to the user, is quite easy. ---
**Author:** ![FernandoTheKoala](https://delvingbitcoin.org/letter_avatar_proxy/v4/letter/f/71c47a/32.png) [@FernandoTheKoala](https://delvingbitcoin.org/u/FernandoTheKoala)\ **Post date:** [September 9, 2025, 7:51am UTC](https://delvingbitcoin.org/t/a-comprehensive-op-return-limits-q-a-resource-to-combat-misinformation/1689/4 "2025-09-09T07:51:36Z")
Thank you for the reply. So basically it is already feasible in an equally easy way, and the “new” op\_return would not change this particular use case in any way. I was confused as it was claimed that using single op\_return of 100KB would have made it easier to visualize the jpeg (much less complicated tools needed to see the image from the hex)