What is BIP-110?
BIP-110 is a proposed change to Bitcoin’s protocol rules on block validity. It is a softfork consensus rule change, meaning that it tightens the rules. Existing nodes will see BIP-110 blocks as valid, however existing blocks may be invalid according to BIP-110 rules.
As BIP-110 is a change to Bitcoin’s protocol rules there is a risk of a temporary or persistent chainsplit and launch of a new coin. Unlike most of the successful softforks in Bitcoin’s past, BIP-110 is controversial and highly contested and therefore the risk of a chainsplit is elevated. In addition to this, some regard an attempt to change the rules without widespread consensus (or while there is significant technical opposition), as an “attack” on Bitcoin and therefore BIP-110 is classified as an attack by some.
On a technical level, BIP-110 tightens the protocol rules in four areas:
- The size of outputs is limited to 34 bytes, with an exception for OP_Return outputs, which are limited to 83 bytes
- Data pushes and witness elements are limited to 256 bytes, with an exception for P2SH redeem scripts
- Spending undefined witness or Tapleaf versions is invalid.
- Certain parts of Taproot are banned, such as annexes, control blocks over 257 bytes and the OP_SUCCESS, OP_IF and OP_NOTIF opcodes in tapscript are banned.
The most popular node software that enforces BIP-110 rules is called Bitcoin Knots and the latest version of this software will enforce BIP-110 after it activates.
The principal aim of BIP-110 appears to be to prevent or deter spam on the Bitcoin blockchain, or alternatively to send a signal against those that support spam on the blockchain. Another key reason for BIP-110 may be to express anger or frustration against Bitcoin Core, due to a perception that this client is not doing enough to fight spam.
Does BIP-110 break some wallets?
Yes. BIP-110 bans some Tapscript options like OP_IF, which is part of miniscript. Wallets that support miniscript can therefore break.
After BIP-110 activates, these wallets will still allow users to generate addresses using tapscript OP_IF that can receive funds. The wallets will then allow users to send funds to these addresses, transactions which are valid under BIP-110 rules. However the funds will then be unspendable and potentially lost forever. Various wallets support miniscript, including ironically, the latest Bitcoin Knots wallet itself.
Does BIP-110 ban certain addresses?
Yes. For example, BIP-110 bans sending Bitcoin to P2PK outputs. (Spending from P2PK outputs is still allowed). P2PK outputs were widely used in the early days of Bitcoin and currently over 1.7 million Bitcoin resides in P2PK outputs. In Bitcoin’s history, a ban like this has never happened before and BIP-110 is therefore highly unprecedented. While it is true that all softforks ban something, typically they are designed to ban activity that has never been widely used or even activity that has never happened before. On the other hand, P2PK outputs are rarely used today.
There are also addresses that may have been generated, where the funds can only be redeemed in ways BIP-110 bans, for instance using OP_IF inside a taproot script. Spending from these addresses is also banned.
Can BIP-110 freeze funds (or enable the theft of funds)?
Yes. BIP-110 can freeze user funds or enable the theft of user funds, but only in certain scenarios. BIP-110 has two built in features to minimise this risk:
- The softfork is temporary. Therefore if your funds are frozen by BIP-110, it is possible that you can wait until the softfork deactivates and then claim back your funds
- Old Bitcoin outputs are “grandfathered in”, meaning that the new restrictive rules are only applied to new outputs created after BIP-110 activates
While the above safeguards do reduce the risk of loss of funds, there are still many ways users could lose funds as a result of BIP-110.
For instance, a user could mistakenly send coins to an output that can only be redeemed using a banned method, such as tapscript OP_IF, after the activation of BIP-110. Our understanding is that the latest version of even the BIP-110 activation client of Bitcoin Knots will not prevent users from doing this, let alone other wallets.
Even advanced users, who know about BIP-110 and prepare for it may be unable to prevent the loss of funds, in the event that they have a combination of characteristics in their transactions, which can make them vulnerable to coin loss despite the safeguards. For instance if using pre-signed transactions, tapscript OP_IF, multiple spending paths and timelocks at the same time, which span the BIP-110 timeframe.
How does BIP-110 activate?
The BIP-110 enforcing clients can activate the enforcement of BIP-110 in one of two ways:
- Via miner signalling in their blocks, with a 55% activation threshold in each two week difficulty adjustment period
- Failing the above, from block 961,632 onwards, expected to be on around 08 August 2026, signalling becomes mandatory for a whole difficulty adjustment period. This mandatory signalling is itself another softfork, a temporary one. Therefore, there is a softfork to activate a softfork. All 2016 blocks in this period must signal in order to reach the state where BIP-110 becomes active
As of today, Farside’s X account will automatically post each time a BIP-110 signalling block is produced, along with a chart showing the latest activation status. After the mining threshold is met, either through 55% or via mandatory signalling, after another difficulty adjustment period known as the grace period, the BIP-110 rules become activated.
Does BIP-110 actually stop spam data?
BIP-110 does stop some but not all of the current ways that spam is put on the blockchain. For instance, inscriptions will largely be blocked, while Runes will largely remain allowed. Proponents of BIP-110 may argue that it’s not about stopping all spam but setting Bitcoin in the right direction, the anti-spam direction.
However, in our view, ultimately, trying to block spam and arbitrary data via banning it, is going to be a losing battle. Arbitrary data can be embedded in fake public keys or even put inside private keys, in such a way that it’s mathematically impossible to block, without also blocking all spending.
In addition, BIP-110 also does not totally ban contiguous arbitrary data either. Please see the below link for examples:
Does spam push up transaction fees for monetary transactions?
This has happened in the past, yes, during waves of spam, for example in 2023. However, most of the spam, for example storing NFTs on Bitcoin, is likely a short term fad. In contrast, Bitcoin as money is a powerful and sustainable use case. People may need to be patient for the monetary use case to power through and eventually outbid other transaction types.
Why is BIP-110 temporary?
The existing BIP-110 clients only enforce the BIP-110 rules for a period of 52,416 blocks (Around one year). After this, the rules lapse. This is said to be in case activating BIP-110 was a mistake. However, it’s possible that what happens is that the debate over BIP-110 is repeated again in 12 months’ time, resulting in further damaging uncertainty over what the Bitcoin rules are going to be.
A softfork that expires in 12 months time is also unprecedented in Bitcoin’s history. Rather than being unsure and testing a softfork on the mainnet, softforks are normally only activated if the technical community is sure it is the best path for the long term. Any testing typically takes place on test networks. The consensus rules of Bitcoin need to be robust, in order for Bitcoin to be an effective money.
Why are people supporting BIP-110?
Proponents of BIP-110 are typically very unhappy about the prevalence of spam on the Bitcoin blockchain. In particular the large amount of data inscriptions, beginning towards the start of 2023. In addition to this, in October 2025, Bitcoin Core changed the default relay setting for OP_Return outputs, increasing the default relay setting from 83 bytes to 100,000 bytes. This change was seen by some as Bitcoin Core signalling support for large spam outputs and made some people antagonistic towards Bitcoin Core.
Rather than merely not applying the new default configuration setting on their nodes, BIP-110 supporters typically want to go further and send a strong signal against the OP_Return relay policy change and against spam. While of course sending a signal against spam is fine, we contend that changing Bitcoin’s protocol rules to send a signal is not an appropriate method for doing so. In order for Bitcoin to succeed as a robust form of money, the protocol rules need to be resilient and not change for these kinds of purposes.
The problem is that if BIP-110 proponents merely responded to the OP_Return relay policy configuration change by not applying the change as their method of sending an anti-spam signal, this is unlikely to have any meaningful impact on conditions on the Bitcoin network. Thereby the signal would be ineffective at reducing the spam, while BIP-110 proponents want to do something more effective against spam.
In our view, it is important to understand Bitcoin as an economic system. Using Bitcoin’s blockchain to store images of cats is a fundamentally stupid and unsustainable way of using the blockchain. The economic value of the cat images will decline considerably over the long term and they already have declined considerably since the boom started in early 2023. In the long term the spammers will stop paying transaction fees and monetary transactions will outbid the spam. In our view, the most effective way of fighting spam is via these economic means. The BIP-110 proponents should instead aim to fight spam by making Bitcoin a better money, pushing up the price of blockspace and thereby driving out spam.
Lessons from the Blocksize War
To us, the key lesson from Bitcoin’s Blocksize War, which raged from 2015 to 2017, is that when there is a significant fight, one should always back the existing Bitcoin rules. This is the only sustainable way to ensure the network converges on one chain and prevents the ecosystem from splitting up again and again into smaller and smaller coins.
Disclaimer: We welcome any corrections to any errors in this article. The information in this article has not been verified and we make no representation or warranty as to its accuracy, completeness or correctness. This material should not be the basis for making investment decisions.
