The Blocksize War The battle over who controls Bitcoin’s protocol rules by Jonathan Bier

The Blocksize War The battle over who controls Bitcoin’s protocol rules by Jonathan Bier

1

First Strike
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.
This war over the blocksize would shatter and split the ecosystem over the
next two years. As the war progressed, it emerged that the struggle was

The Blocksize War The battle over who controls Bitcoin’s protocol rules by Jonathan Bier