Alarmists warn the Bitcoin blockchain will soon become home to child pornography. Learn when

Bitcoin is known as a censorship-resistant network. Normally, this characteristic is presented as one of its basic selling points. The Bitcoin dev community is stirred with a heated debate over the imminent removal of a spam filter that limits non-monetary data to 83 bytes per block. Opponents claim it will allow the posting of child porn on-chain, effectively making Bitcoin illegal in most jurisdictions.

Bitcoin Core vs. Bitcoin Knots

Blockchain data is monitored and verified by the nodes. Each block may contain up to 83 bytes for non-monetary data (for instance, images). This opportunity is possible via an OP_RETURN script. Some call it a spam filter as they believe it helps the Bitcoin network (BTC) to be used precisely for monetary transactions. OP_RETURN prevents the network from getting flooded with arbitrary data (non-monetary data). Spam filter removal opponents say the change may result in network congestion. 

However, some developers are advocating for the removal of a spam filter, thus expanding the arbitrary data limit to around 2 megabytes per block. The reason for this change, cited by these developers, is dismantling restrictions and censorship. It opens gates for various use cases like sharing JPEG files, videos, documents, etc. 

A more technical excuse is that images and other non-monetary data already have a place on the Bitcoin blockchain. Such data is posted as forever unspent transaction outputs, making the blockchain bloated and reducing the transaction speed. The proposal aimed at removing the arbitrary data limits was introduced by Peter Todd earlier this year.

The proponents of the spam filter removal are the community behind the Bitcoin Core software, the oldest and most popular node program. They achieved consensus, so the Bitcoin Core version 30 that increases the OP_RETURN space up to the entire block is scheduled to be released in October 2025. Given that the majority of blocks are verified using Bitcoin Core software, after the October update, the Bitcoin network will probably get much arbitrary data on it. Those who oppose the filter remover mostly use Bitcoin Knots nodes. 

While the debate persisted and many of those using Bitcoin Core decided to transition to Bitcoin Knots, the removal of the spam filter was approved and scheduled for October 2025. The proponents of the spam filter removal say that those not satisfied with an update can use an old version of the software or switch to a different one.

The fallout of the debate got personal and pretty aggressive. At some point, personal attacks on X made one of the principal Bitcoin Core devs, Gloria Zhao, temporarily delete her account. Some critics accused Bitcoin Core devs of serving the interests of Citrea, a zero-knowledge Layer 2 rollup protocol, allowing the use of Ethereum-like functions on the Bitcoin blockchain. One of the Bitcoin devs, Bitcoin Mechanic, claims he was blocked on GitHub after criticizing Bitcoin Core’s plans. 

The reason for such a harsh pushback against Peter Todd’s proposal is that Bitcoin Core is a very influential software. At the time the proposal was made, it was responsible for around 99% of all the Bitcoin blockchain data. As the conflict continued, over 15% of the Bitcoin Core community opted out to become Bitcoin Knots runners.

Illegal content concern

It was Bitcoin Mechanic who reignited the debate on Aug. 31, when posting an hour-long video on his YouTube channel and on X. In the video, he claimed that the spam filter removal will draw “unforeseen consequences,” meaning that content like child pornography can appear on the Bitcoin blockchain following the Bitcoin Core v30 update in October. Bitcoin Core supporters cite other blockchains without spam filters as proof that child pornography is not going to infiltrate the blockchain. 

Given that Bitcoin’s ledger is immutable and censorship-resistant, it will mean that the illegal content will stick around there forever, turning Bitcoin into a storage of illegal content. Unlike monetary data, whether it was involved in selling illegal stuff or not, is neutral, according to Bitcoin Mechanic, arbitrary data itself may turn out to be “something you just discriminate against, depending on what it contains.” 

Bitcoin Mechanic admits that the “disgusting content” was already uploaded on the Bitcoin blockchain in 2013. It has the form of an inscription. However, he says, the current structure allows bitcoiners to avoid any connection with this data by not using inscriptions. In contrast, the illegal content that potentially can be uploaded after the Bitcoin Core update will be available not in a hex form. 

The topic of Bitcoin and child pornography is not new. It was extensively covered in 2017. At that time, the spam filter worked well, so alarmists had to admit they were not right. But today we are having a different problem, as the data per block is increasing. They say nations and countries may prefer to ban Bitcoin altogether, as running a node would become equal to storing illicit content on your computer. Legally, this concern requires experts’ research, while morally, it is already seen as unacceptable by some in the Bitcoin community. 

Such a heated battle is nothing new for the Bitcoin space, as this system is decentralized and community-driven. History has already seen the clashes over block size and inclusion of ordinals. As the Bitcoin Core update is imminent, we’ll learn how big the problem is in the following months.