Bitcoin Unlimited (BU) is a full node implementation for the bitcoin and Bitcoin Cash networks. The

Bitcoin Core Bitcoin (abbreviation: BTC; sign: ₿) is a decentralized digital currency that can be transferred on the peer-to-peer bitcoin network. Bitcoin transactions are verified by network nodes through cryptography and recorded in a public distrib ...

client, from which Bitcoin Unlimited is forked, has a hard coded one megabyte block limit; Bitcoin Unlimited differs by allowing users to signal which block size limit they prefer, find the limit having a majority consensus and automatically track the largest proof-of-work, regardless of block size. However, if a block greater than one megabyte in size is accepted by Bitcoin Unlimited and rejected by nodes with a block size limit, a

fork In cutlery or kitchenware, a fork (from la, furca 'pitchfork') is a utensil, now usually made of metal, whose long handle terminates in a head that branches into several narrow and often slightly curved tine (structural), tines with which one ...

of the network will occur, resulting in two separate blockchains with Bitcoin Unlimited nodes following the chain with the largest proof-of-work. The release of Bitcoin Unlimited follows the release of Bitcoin XT and

Bitcoin Classic Bitcoin forks are defined variantly as changes in the protocol of the bitcoin network or as the situations that occur "when two or more blocks have the same block height". A fork influences the validity of the rules. Forks are typically conduct ...

, alternative proposals which aimed to increase bitcoin's transaction capacity of around 2.5-3 transactions per second by increasing the hard-coded block size limit. As of version 1.1.0.0, Bitcoin Unlimited releases are compatible with Bitcoin Cash, a cryptocurrency that split from bitcoin and allows larger blocks.

Scalability

Bitcoin Unlimited is an attempt to upgrade

into a client that processes bitcoin transactions into blocks with a potential maximum size greater than the Core's

hard-coded Hard coding (also hard-coding or hardcoding) is the software development practice of embedding data directly into the source code of a program or other executable object, as opposed to obtaining the data from external sources or generating it at ...

limit of one megabyte. The one megabyte block size limit was added in 2010 by

Satoshi Nakamoto Satoshi Nakamoto is the name used by the presumed pseudonymous person or persons who developed bitcoin, authored the bitcoin white paper, and created and deployed bitcoin's original reference implementation. As part of the implementation, Nakam ...

as a temporary anti-

DoS DOS is shorthand for the MS-DOS and IBM PC DOS family of operating systems. DOS may also refer to: Computing * Data over signalling (DoS), multiplexing data onto a signalling channel * Denial-of-service attack (DoS), an attack on a communicat ...

measure. This limited the maximum network capacity to about three transactions per second. Per the advocates of the change, a block size increase is needed in order to avoid a workflow

bottleneck Bottleneck literally refers to the narrowed portion (neck) of a bottle near its opening, which limit the rate of outflow, and may describe any object of a similar shape. The literal neck of a bottle was originally used to play what is now known as ...

due to the number of transactions made as bitcoin adoption increases. With Bitcoin Unlimited, miners are independently able to configure the size of the blocks they will validate. Miners using Bitcoin Unlimited continue to process regular-sized blocks but as soon as a block larger than one megabyte is mined, they will follow the chain containing the most work. Per the Bitcoin Unlimited website, the

scalability Scalability is the property of a system to handle a growing amount of work by adding resources to the system. In an economic context, a scalable business model implies that a company can increase sales given increased resources. For example, a ...

solution will be found at a focal point.

Support

Bitcoin Unlimited follows the release of Bitcoin XT and

, alternative proposals on how to increase bitcoin's transaction capacity. Mining pools including Antpool.

Opposition

Developers of Bitcoin Core have been reluctant to increase the block size limit. BU nodes were attacked after developers brought a bug to light on 14 March 2017. The numbers of nodes hosting Unlimited fell from 780 to about 370 following the attacks, the lowest level since October, and returned to about 780 within 24 hours according to website coin.dance which tracks network data. As of July 2022, there are only three BU nodes online according t
Coin Dance
data, a decrease from seven in May 2021.

Notes

References

External links