The Blocksize War: The battle over who controls Bitcoin’s protocol rules

The “Blocksize War” was a multi-year debate within the Bitcoin community about the optimal size of blocks on the Bitcoin blockchain. The debate centered around whether to increase the block size from 1MB to allow for more transactions per block, thereby increasing the transaction capacity of the Bitcoin network.


“The Blocksize War: The battle over who controls Bitcoin’s protocol rules” is a book written by Jonathan Bier, which delves into the history of the conflict over the block size limit in Bitcoin. The book provides a detailed account of the events that took place during the Blocksize War, including the arguments put forward by both sides, the key players involved, and the various proposals that were put forward to address the issue.

The book explores the philosophical and ideological differences that underpinned the debate, as well as the technical aspects of the block size limit and the implications of changing it. It also looks at the wider implications of the Blocksize War for the future of Bitcoin and the cryptocurrency industry as a whole.

The blocksize debate was a pivotal moment in Bitcoin’s history. It demonstrated the importance of collaboration, compromise, and open dialogue in advancing the development of the world’s most important decentralized network.

The book, “The Blocksize War” provides a comprehensive and insightful analysis of one of the most significant conflicts in the history of Bitcoin, shedding light on the challenges of governance and consensus-building in decentralized systems.

It was Saturday, August 15, 2015, when an event occurred that took many in the Bitcoin space by surprise and shook the community to its core. Two of the most prominent and respected Bitcoin developers at the time, Mike Hearn and Gavin Andresen, had respectively released and thrown their support behind a new, incompatible version of Bitcoin. This new client was called Bitcoin XT. Bitcoin had offered such hope, excitement and opportunity to many, and it now appeared as if this act was sure to send the system into disarray, peril and potential catastrophe. As the Guardian newspaper said on the following Monday:

“The Bitcoin wars have begun.”

On the surface, the war appeared to be centred on just one reasonably narrow issue, the maximum size limit for the blocks which make up Bitcoin’s blockchain. Bitcoin XT was a proposal to increase the amount of space available in blocks. In 2015, the blocksize limit was 1 MB and Bitcoin XT wanted to increase this limit to 8 MB and then double it every two years until 2036, when the limit would be around 8,000 MB. The reason for this was that blocks were becoming larger as the system became more popular, and the blocksize limit was close to being reached, which would result in full blocks. Proponents of the increase argued that higher capacity was needed to ensure Bitcoin could scale up and become a cheap global payments system. They were concerned that, if the limit was regularly reached, this would make the network difficult to use and too expensive, which would damage the growth prospects for the system. To Gavin and Mike, we were heading into a crisis, where users could be turned away from the network, and action was required. Gavin and Mike’s opponents were concerned by the release of the incompatible client, fearing it could split the network into two, causing chaos and confusion.

More Information

Additional information


Jonathan Bier

Year of Publication









There are no reviews yet.

Be the first to review “The Blocksize War: The battle over who controls Bitcoin’s protocol rules”

Join our monthly newsletter

Be in the know, receive exclusive offers by joining our email list.