Yesterday (22), the Bitcoin Core development team officially confirmed that they would remove the 80-byte limit on OP_Return opcodes in version 30.0. Bitcoin developer and advocate Jimmy Song strongly criticized Bitcoin Core for this move, saying it was essentially a "fiat currency mentality."

The development team ignored the voices from the Bitcoin community and node operators

OP_Return is a special output format in Bitcoin transactions that allows small amounts of data to be written to the blockchain. It is primarily used to store small amounts of information on the Bitcoin blockchain without affecting Bitcoin's functionality. However, unlike regular transaction outputs, OP_Return outputs cannot be spent and do not increase the burden on the set of unspent transaction outputs (UTXOs).

It can be said that OP_Return allows Bitcoin to be used not only as a currency, but also as a tool for data storage and verification, while also providing a foundation for the development of other assets and applications. For example, it was widely used during the Ordinals inscription craze in early 2024.

OP_Return was proposed by the Bitcoin developer community in 2014. Its original purpose was to allow transactions to securely carry small amounts of data on the blockchain. The typical upper limit was 40 bytes, later increased to 80 bytes in v0.11. The original intention of this feature was to allow users to leave a brief message on the Bitcoin chain (such as proof of ownership, digital file hashes, copyright notices, and artwork evidence), while preventing non-monetary uses from occupying UTXO space and maintaining a clean ledger.

The decision to remove the OP_Return opcode led Jimmy Song to accuse Core developers of avoiding users' concerns about removing the OP_Return limit (currently 80 bytes) and ignoring strong opposition from the Bitcoin community and node operators.

Many opponents worry that without the massive influx of financial data, the size of the blockchain will expand rapidly, raising hardware costs and weakening the foundation for "everyone to run a node."

Song said: "The idea that spam is difficult to define and therefore should not be distinguished in software design is a waste of time and political sophistry. The non-monetary uses of Bitcoin are spam."

The debate over OP_Return has been going on for nearly six months, inevitably reminding the market of the Bitcoin block size dispute between 2015 and 2017. The dispute eventually led to a hard fork of the Bitcoin protocol and the birth of Bitcoin Cash. This has led some in the Bitcoin community to speculate whether the OP_Return dispute will also trigger a similar split.

In 2017, the community was unable to reach a consensus for a long time, which eventually led to a hard fork.

Between 2015 and 2017, the Bitcoin community was divided into "big block" and "small block" advocates due to a heated debate over the 1MB block size limit. The former sought to modify the original Bitcoin protocol to increase block capacity to handle more transactions, arguing that cheaper and faster transactions would make Bitcoin more scalable.

The latter group wants to maintain the 1MB block size limit (Satoshi Nakamoto originally added an explicit 1MB block size limit to each block, never publicly explaining why it was added) to prioritize Bitcoin's fundamental principles of security and decentralization. They believe that if the block size is increased, it will make it more expensive for ordinary users to run Bitcoin nodes, which will in turn lead to businesses hosting nodes in data centers, undermining the network's decentralization.

After prolonged disagreements failed to reach consensus, a hard fork ultimately occurred. On August 1, 2017, those supporting block expansion created a new chain, Bitcoin Cash, which raised the block size limit to 8 MB, later expanding it to 32 MB. BTC (Bitcoin) maintained its original 1 MB block size limit, shifting its focus towards its role as "digital gold" and store of value. BCH focused on payment applications and high-speed, low-cost everyday transactions.

It has laid the foundation for BTC to be equivalent to digital gold (high security, value storage) and BCH to be equivalent to circulating currency (fast, low cost), and has also directly affected subsequent Bitcoin governance, protocol disputes and other fork discussions.

The villains are leaving in large numbers and turning to Bitcoin Knots

Many node operators are now turning to Bitcoin Knots, which maintains existing data limits. According to Coin Dance data, the percentage of nodes using Bitcoin Knots has skyrocketed from approximately 1% in 2024 to 20%, a dramatic increase in just nine months. Knots allows node operators to enforce strict data size limits, which supporters believe is necessary to maintain the decentralization of the Bitcoin protocol.

Since the decentralized protocol's creation in 2009, the Bitcoin ledger has generated approximately 680 GB of data. This is due to Bitcoin's simple architecture and strict data limits. Bitcoin's low data storage requirements allow anyone to synchronize approximately 680 GB of full-chain data with retail hardware costing approximately $300, significantly promoting democratized participation and maximum decentralization.

This time, node operators took concrete action to resist, switching to Bitcoin Knots on a large scale, triggering a historic exodus.

Developers who support removing the OP_Return limit believe that the existing 80-byte limit is just an artificial threshold. In fact, there are already many ways to bypass it. For example, using the Taproot and Ordinals technologies in the Bitcoin protocol upgrade to split the data and embed it into different parts of the transaction, breaking through the size limit of a single OP_Return. If the data carrying capacity can be increased, it can also inspire more innovative applications, thereby supporting the sustainable development of the network.

This debate over the OP_Return restriction highlights the challenge the Bitcoin community faces in balancing on-chain data storage space with the principle of decentralization. With the evolution of technology and the diversification of use cases, the 80-byte limit no longer effectively reflects real-world needs. Removing this restriction signifies a more open and inclusive phase for the Bitcoin ecosystem, fostering more innovative applications and generating new revenue streams for miners.

However, this also brings the risk of network expansion and decentralization pressure, forcing the community to re-examine how to find a balance between expansion and protecting core values.