So some people here appear to believe spam on bitcoin is not a serious or important problem. I'm here to explain why bitcoin spam is a very big problem right now. But before I start, I should clarify some terms:
- I define spam as any non-monetary data on bitcoin. Runes, BRC tokens, ordinals, rare sats, inscriptions, you name it. If Murch, Shinobi, Gloria, or anyone else is confused, please tell them to come here and I will work best to explain. Bring your own crayons and paper.
- Spam UTXO are UTXOs with less than 1000 sats, intended for spam data storage. These people have to put some sats in it to pass it off as a genuine bitcoin transaction. So they put just a little above the dust limit. It's important to understand that these people are cheating the system by using it in a way that it was not intended to be used. Almost all, over 99.99% of fake pubkeys and fake scripthash are spam UTXOs. These people are attackers, not users.
- Censorship: It's important to understand that bitcoin is money. As such, preventing you from posting jpegs with fake pubkeys, fake scripthash, or fake witness does not qualify as censorship anymore than stopping you from preaching about Allah in a Jewish temple is a form of religious censorship.
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Until 2023 spam was not really a thing. A few people would embed some inscriptions like bible verses, the white paper, or other random but rare messages. But since early 2023, the chain blew up with spam and the UTXO set basically doubled in 3 years. There are two aspects of the spam problem: the social aspect, and the on chain aspect:
Social aspect:- Before 2023, pretty much everyone understood what spam was. But gradually, some people started to legitimize spam by saying thing like "those are valid transactions" or "they paid they miner fees" or referring to them as "users", not attackers. This is similar to staying the Nigerian prince email you received is a valid email that followed all the email protocols, proper grammar and syntax, and the sender paid his internet bill. Even some core contributors have referred to spam as "new use cases". In 2012 when someone posted child p**n on chain, nobody dared ask if it was a valid transaction, or if he paid his miner fee. We all recognized it as an obvious attack, but the language around spam is changing in an Orwellian manner.
- Feb. 2022 -
Core changes the documentation on Github. The description of "Bitcoin as an experimental digital currency that enables instant payments to anyone, anywhere in the world." is changed. It's replaced with the definition of Bitcoin core and all mentions of bitcoin as money or currency have been removed from the documentation.
- Luke Dashjr submits
a pull request. Effectively a way to filter out ordinals. The definition of datacarriersize is changed in the core documentation. Some spam apologists complain of censorship, and the pull request is closed based on it being too controversial, and based on the new definition of datacarriersize. Had core implemented this filter in their next release, over 85% of the nodes would be running this filter today.
- Gloria Zhao, core head maintainer,
openly insults bitcoiners who don't believe in altcoins,
gives the thumbs down to bitcoin maximalists, and the thumbs up to NFTs. She admits
she doesn't know or care about economics, or bitcoin as money, and she refers to
spam as "uses cases we have today" she feels Satoshi failed to account for. She also reduces the subject of spam down to
you liking or disliking cat pictures.
- Previously respected people like Maxwell, Back, and others are now going around and attacking any and all attempts at fighting spam as futile, censorship, confiscatory, and attacks on bitcoin, Yes friends, spam is no longer an attack to them, but resisting the spam is the real threat here based on Back, Maxwell et al. These bad actors are now campaigning against all attempts to fight spam.
- An entire industry is being erected around bitcoin spam.
ordiscan,
ordinalexplorer,
oklink, and
countless other spam explorer sites and spam indexer sites are popping up. There are now more bitcoin spam explorers than there are actual genuine bitcoin explorers, And new ones are popping up all the time.
- June 2025:
Core releases a statement about the op_return filter controversy. In it they explain: "Knowingly refusing to relay transactions that miners would include in blocks anyway forces users into alternate communication channels, undermining the above goals."
This indicates core doesn't really have a problem with spam of any kind. They don't think that miners filling their blocks with 30% of absolute crap is a problem, because miners accept a fee for it.
According to core, the problem is that nodes might filter spam, and not cater to the miners. If you run a node, you are the problem unless you bend to the desires of bad actor spam miners.
On chain aspect:- The UTXO set is blowing up with 40-50% of all UTXOs being spam UTXOs with fewer than 1000 sats, just above the dust limit. Almost all of them created in the last 3 years. And though they make up half of the UTXO set, they only constitute less than 0.002% of the total bitcoin in circulation.
- After 3 years of an ongoing spam attack, and not doing anything about it, barely recognizing it as a problem. core decides to remove a spam filter. A filter that has been in place for 11 years is suddenly framed as a form of censorship, and core shills claim the filter "doesn't work" because only 99.9% of the op_return transactions are within the filters limits and/or because spammers use other methods to spam bitcoin. This is like saying your front door lock failed to work because an intruder used the unlocked back door.
- With the release of core 30, file sharing is effectively a new supported and sanctioned use case of bitcoin. Spammers no longer need to cheat the system to spam bitcoin with fake pubkeys, fake scripthash, or fake witness. They can now upload any and all explicit/illicit/illegal/immoral file they desire. No need to go through a 3rd party spam miner anymore. They can put any file they desire on the 90,000 nodes of the network, and they are using bitcoin EXACTLY as core 30 intents them to use it.
- During the last halvening, runes spam swamped the blocks and pumped miner fees to over $100 for one block confirmation, For weeks, real bitcoin transactions were displaced by spam scams. This should put to rest the absurd idea that "miner fees will displace spam" as if some magic smoke in the fees wold displace only spammers but not real bitcoin monetary transactions.
- Currently, as I write this, some bad actor mining pools are lowering their miner fees to below 1 sat/vB in order to fill their blocks with spam inscriptions. Further discrediting that the fees are the filter to spam. And estimated 1 million inscriptions are being mined every week by these disgraceful miners who are "making spam cheap again".
- New on chain services like SlipStream and LibreRelay are launched. These services are expressly tailor made to help spam miner accept more spam.
Q&A:Q: So what? You still can send and receive bitcoin, no?
A: It's important to realize that the health and survival of bitcoin depends on a large number of nodes regulating the network. With devs and mining pools getting increasingly and dangerously centralized, the nodes network is the only aspect of bitcoin that is still decentralized. This is something unique to bitcoin in comparison to all other "crypto". As such, nodes are being burdened to store spam they have no incentive to store. This spam constitutes a direct threat to the ability of running a node affordably, and without any added moral/social/legal risks that this spam can burden nodes with. Th survival of bitcoin as a decentralized currency depends on a large umber of nodes regulating the network. Don't let naysayers fool you into thinking running a node is basically useless and a selfish and powerless endeavor. You should run a node too, preferably Knots, not core as they are now a bad actor on the network.
Q: What do you care? Just ignore them and they will go away.
A: This is incredibly naive. With core effectively beating down a path for spam, and an entire infrastructure being built around spam (see above) spam will only get worst and new spam schemes will arrive on bitcoin unless we do something about it.
Q: Data is freedom, fighting arbitrary data could be a form of censorship?
A: No, bitcoin is money and bitcoin is built to provide you with censorship resistant money. Your right to religion, abortion, and jpegs don't belong on bitcoin anymore than your right to watch porn or worship Islam belong in my church. You can use bitcoin to buy a pancake or a jpeg. But neither your pancake nor your jpeg belong on the bitcoin chain. Other shitcoins are built expressly to flex your right to dickbutt jpegs. Go there.
Q: Child p**n and other illicit stuff happened before and bitcoin survived. Why don't you go away?
A: Yes, child p**n and other stuff happened in the past. We were all furious about it. We all wanted to find ways to minimize or remove it. We did not build services like OpenRelay or SlipStream to cater to more of it. We didn't say it's a valid transaction, we didn't care if a miner fee was paid or not. We recognized it as an attack, not as an "exiting new use case". And the offensive material was broken up in many transactions, obfuscated to look like genuine bitcoin transactions. It was not a contiguous file the network was expressly modified to accept as a sanctioned and supported use case. And we certainly didn't blow up filters to invite more of it. On the contrary, more filters were built after the first instance of child p**n on bitcoin.
Q: I've been told core devs don't like spam. Aren't you overreacting?
A: Don't follow what they say, follow what they actually do, They call it "arbitrary data" or "new use case" because it sounds better than spam when describing a dickbutt jpeg. They have resisted any and all measures against spam, and they are removing filters, changing defaults to facilitate more spam. And most often claiming they can't do anything about it, or they shouldn't do anything about it.
Q: But we can't stop them, they are smarter and motivated, Why bother?
A: The demand world wide for redundant and permanent cheap data storage us virtually unlimited. It's our duty, all of us, to protect bitcoin against it and minimize the incentives and effects on bitcoin. More hostility towards spam will result result in less spam, with the implied understanding that it can never be completely stopped.
Q: Isn't that a slippery slope towards censorship?
A: No, since the start of bitcoin, spam was always resisted and treated in an hostile manner. There are over a dozen filters in core, all mostly present since the start. None of them ever devolved into censorship. And as new spam cases arise, new filters should be built, not removing existing filters. And you have to give the 90,000+ bitcoiners who run a node some credit. We understand the difference between a dickbutt jpeg and blocking Iranian UTXOs. We can tell the difference between an ordinal and an OLFAC compliant list of UTXOs.
