How Bitcoin Nearly Got Bigger Blocks in 2015

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  • Bitcoin’s block size has been debated since blocks filled up in 2015
  • The fierce battle from 2016 to 2018 would have been avoided if one of two competing BIPs proposed in 2015 had been adopted
  • These proposals could have significantly changed Bitcoin’s current landscape if implemented

Bitcoin’s block size has been a source of debate ever since the blocks started to fill up in 2015, which represents the origins of the blocksize war. However, the fierce battle that was waged between 2016 and 2018 would have been avoided had one of two competing Bitcoin Improvement Proposals (BIPS) been adopted back in the pre-war days. But what were these proposals and what would Bitcoin look like now if one of them had triumphed? Let’s find out.

Miners’ Choice

The first of the two competing BIPS arrived on June 11, 2015, when Bitcoin developer Jeff Garzik proposed BIP 100. BIP 100 dealt with the scaling problem through a flexible and adaptive method, allowing miners to vote on the maximum block size, with the size being adjusted based on the majority vote.

Every 2016 blocks, which roughly equates to two weeks, miners could signal their preferred block size, which would then be adjusted according to the median of these votes, up to a limit of 32 MB. This proposal aimed to make the block size more responsive to real-time network conditions and miner consensus, providing a decentralized and dynamic solution to scalability.

However, BIP 100 was criticized over its potential for centralization, its technical complexity, and potential issues surrounding economic stability and governance. Larger block, it was argued, could lead to centralization, as they might favor miners with greater resources and higher bandwidth capabilities, which could marginalize smaller, individual miners, making it more challenging for them to compete effectively. 

Andresen Suggested Two-yearly Doubling

One of the biggest critics was influential Bitcoin developer Gavin Andresen, and 11 days after the submission of BIP 100 Andresen put his his own solution forward. BIP 101 recommended a dramatic increase in the maximum block size from the existing 1MB limit to 8 MB, but that was just the start; Andresen wanted the block size to double every two years until 2036, eventually reaching a maximum size of 8 GB.

The proposal also included an activation mechanism that relied on miner support. It specified that 75% of the last 1,000 blocks would need to signal their support for the increased block size before it could be implemented. This approach aimed to ensure that a significant majority of the network’s miners agreed with the change, thereby facilitating a smoother transition.

However, BIP 101 had its own critics, with the opposition falling along similar lines as BIP 100 concerning centralization and the actual act of voting.

Nobody Wins

Advocates and critics of each proposal duked it out for months, but despite their merits and best intentions, neither BIP 100 nor BIP 101 gained the necessary consensus for implementation. As a result, the community remained deeply divided over the best approach to scaling, leading to Segregated Witness being implemented in 2017, which led to a complete absence of on-chain scaling and the creation of Bitcoin Cash.

Had either BIP 100 or 101 won out in the early skirmishes of the block size war then things, including Bitcoin’s block size, would have been very different indeed. The debates and proposals of 2015, including BIP 100 and BIP 101 among other suggestions, played a crucial role in shaping the future of Bitcoin, highlighting the complexities and trade-offs involved in scaling a decentralized network, paving the way for the solutions that were eventually adopted.