Bitcoin Unlimited

For Bitcoiners, a persistent question surrounding Bitcoin is the issue of block size. Bitcoin Unlimited seeks to resolve this contentious issue by doing away with Bitcoin’s maximum block size parameter altogether. This article explores Bitcoin Unlimited in detail and explains why it provides a better solution for Bitcoiners everywhere. Visit for complete and authentic information. 

Bitcoin Unlimited (BU) is an alternative Bitcoin client to Bitcoin Core, the original Bitcoin software created by Bitcoin’s inventor Satoshi Nakamoto. Bitcoin Unlimited allows users to configure their own preferred block size limit within their node, rather than having a one-size-fits-all limit hardcoded into Bitcoin software.

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An open letter signed by some of Bitcoin’s most prominent developers says that Bitcoin Unlimited would simply be too risky for the wider community to accept it as an upgrade. They cite concerns about attacks on the network or using spinning up capacity not being met with supplying actual resources which could lead to miners blocking transactions even though the nodes are able to handle them.

The BU team argues that it can scale on-chain and will allow Bitcoin to become a global transaction network capable of handling the same transaction volume as major credit card companies. Bitcoin Unlimited has received support from Bitcoin exchanges, industry members, and mining pools including Bitfinex, Bitfury,, Bitcoin XT, BTCChina, Bumble Bee Mining, The Rock Trading, and ViaBTC.

Bitcoin Unlimited follows both SegWit (BIP141) which changes maximum block sizes to be smaller but better able to handle them by implementing a hard fork 3 months after lock-in; and Bitcoin Classic’s 2-4-8 or even 8 MB blocks with no flag day hard fork which increases maximum block size immediately upon activation.

Although BU does not require 95% miner signalling like SegWit currently requires before it activates on the Bitcoin blockchain, Bitcoin Unlimited requires that 75% of miners are running the Bitcoin Unlimited software before it activates. This ensures that if BU does activate, no minority chains will survive because they would not be able to maintain the necessary hash rate for security.

The Bitcoin Unlimited client can be configured to allow larger block sizes than just 8 MB as it is possible the Bitcoin network could even handle 1 GB blocks in time, although this has never been tested. Bitcoin XT was one of Bitcoin’s earlier attempts at increasing Bitcoin’s maximum block size beyond 1MB with BIP101 which proposed 8 MB blocks but did not have sufficient uptake. Bitcoin Classic simply raised the maximum block size to 2 MB without attempting a fork at all. Bitcoin Unlimited takes this middle path by allowing nodes and miners to configure their own block size limit up to whatever Bitcoin can handle before the next difficulty retarget. The Bitcoin Unlimited mainnet is currently at 16MB blocks with no reported issues, although it has not yet reached full activation because only around 40% of Bitcoin miners are signalling support for Bitcoin Unlimited at the time this article was written.

New transactions are now being successfully mined into Bitcoin Unlimited’s 16 MB testnet blocks at 250 kWh/block which is one-quarter of what Bitcoin consumes today. This improvement in efficiency will allow even lower cost mining if Bitcoin ever does start requiring $0.10/kWh instead of $0.20/kWh like it does today so long as Bitcoin price continues to rise faster than electricity costs. If Bitcoin Unlimited becomes Bitcoin’s main software, Bitcoin’s blockchain could one day handle over 500 transactions per second.

Now that SegWit has successfully activated, Bitcoin Unlimited is no longer necessary to achieve the same goal of increasing Bitcoin’s block size limit because it will also be achieved by SegWit. BU can still play an important role in ensuring Bitcoin’s future scalability if the mining community chooses not to activate BIP148 and continues to mine larger than 1MB blocks. By choosing not to signal for Segwit after SegWit activates on August 21st or later, any miner can prevent activation of Segwit while allowing their own nodes to accept larger blocks up to 2 MB once Bitcoin Unlimited activates something it allows them to do via a flag day hard fork.

Many Bitcoin Core devs fear Bitcoin Unlimited because it does not include a “malicious” upgrade mechanism like BIP9 soft forks which have been used to successfully activate Segregated Witness and other improvements in Bitcoin Core. The Bitcoin Core proposal known as UASF or User Activated Soft Fork is scheduled for August 1st, 2017, and Bitcoin Unlimited is afraid that the Bitcoin mining community will not realise Bitcoin Core’s BIP148 is a USAF until it has already happened and Bitcoin Core would have activated SegWit with its own BIP9.

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