Gavin Andresen Publishes BIP 101Gavin Andresen Publishes BIP 101

On June 22, 2015, the man Satoshi Nakamoto chose to lead Bitcoin published a proposal that split the community down the middle. It never activated. The argument it started never ended.

Who Gavin Andresen WasWho Gavin Andresen Was

Andresen's position in Bitcoin was unique. Satoshi personally handed him stewardship of the project before disappearing in 2010, making him the first person outside Satoshi with commit access to Bitcoin's codebase. When Andresen spoke, it carried more weight than any other developer's opinion. When he formally proposed changing Bitcoin's block size limit, it wasn't a fringe idea from the community. It was the de facto leader of Bitcoin development declaring that the status quo was wrong.

The Problem He Was Trying to SolveThe Problem He Was Trying to Solve

By mid-2015, Bitcoin blocks were regularly hitting the 1MB limit. TradeBlock estimated blocks were reaching capacity at least four times daily, and fees were climbing. Andresen had been arguing publicly for months that the limit needed to go. On June 22, he formalized it as BIP 101.

The proposal was straightforward in concept: replace the fixed 1MB limit with one that grew mathematically over time. Start at 8MB in January 2016, then double every two years for twenty years, reaching 8,192MB by 2036. The doubling schedule was explicitly modeled on long-term trends in CPU power, storage, and bandwidth — the assumption being that what seemed large today would be routine in two years.

The Chinese Miners DetailThe Chinese Miners Detail

The initial proposal called for 20MB, not 8MB. Andresen reduced it to 8MB after consulting Chinese mining pools about their bandwidth constraints, specifically the effect of the Great Firewall of China on data speeds. This detail matters: he was building consensus with miners rather than with the developers who maintained Bitcoin Core. The two groups he needed to convince were already operating in different conversations.

How Core RespondedHow Core Responded

Bitcoin Core developers were unmoved. A note attached to the GitHub pull request for BIP 101 stated plainly that there was "a near zero chance of this getting merged." The two camps were talking past each other: one side saw a technical emergency that would strangle Bitcoin's growth, the other saw a hard fork change too risky and too irreversible to rush.

Bitcoin XTBitcoin XT

Rather than wait for a consensus that wasn't coming, Andresen and Mike Hearn implemented BIP 101 in Bitcoin XT, a fork of Bitcoin Core, which went live on August 15, 2015. The activation condition: 75% of the last 1,000 mined blocks must signal support. That threshold was never reached. Bitcoin XT peaked, then collapsed. BIP 101 was eventually removed from it entirely.

Two Years of Civil WarTwo Years of Civil War

What followed was two years of escalating conflict. Bitcoin Classic. Bitcoin Unlimited. SegWit2x. One by one, proposals to raise the block size either failed to activate or collapsed before launch. Each attempt deepened the fracture. The debate never resolved, it just changed form.

The one attempt that produced a permanent split was Bitcoin Cash in August 2017. A portion of the community that had been arguing for larger blocks since 2015 forked away rather than accept SegWit, taking BIP 101's core argument with them.

Andresen's FallAndresen's Fall

Andresen did not emerge from the block size wars intact. In May 2016, while the debate still raged, he publicly endorsed Craig Wright as Satoshi Nakamoto. The Bitcoin community rejected the claim unanimously. Shortly after, his commit access to Bitcoin Core was revoked. The man Satoshi had chosen to lead Bitcoin ended up outside the project he had stewarded for six years.

Where Things StandWhere Things Stand

BIP 101 is listed as Closed on GitHub. The base block size Andresen tried to raise still stands. Bitcoin's answer to the scaling question turned out to be SegWit in 2017 and the Lightning Network built on top — scaling upward rather than outward, without the hard fork and without the centralization risks that larger blocks would have introduced.

Primary sources: BIP 101 | Bitcoin Core pull request #6341

Part of an ongoing series on Bitcoin history. This event falls on June 22, 2015.