Jeff Garzik’s Proposal On The Blockchain Debate: 2 MB Blocks

blockchain debate Jeff Garzik

Jeff Garzik, known for significant code contributions to the Bitcoin reference client (Bitcoin QT / Core) and his Bitsat project, which aims to put Bitcoin nodes into orbit, recently submitted Bitcoin Improvement Proposal (BIP) 102 to address the blockchain debate over block size.

Jeff Garzik image
Jeff Garzik

As you probably know, Bitcoin transactions broadcast over the network are compiled by miners into a distinct block about every 10 minutes. In Satoshi’s original implementation, the number of transactions per block was unlimited but this was later patched to a 1 megabyte ceiling to prevent spam attacks. BIP 102 seeks to double this limit to 2 megabytes, effective on the 11th of November, 2015.

Why the Debate

While it may sound like a “miner” change, this would necessitate a hardfork of the Bitcoin network. Old and new versions of Bitcoin software will therefore become incompatible, meaning that without consensus on the switch, the Bitcoin network may become divided with potentially destructive consequences.

Proponents of the change insist that the benefit outweighs the risk as, without such a block size boost, Bitcoin will be unable to scale to incorporate an influx of new users and/or certain blockchain-dependent services. Advocates of the status quo argue that the current limit promotes decentralisation and stimulates the emergence of a market for transaction fees; transactions which don’t pay a sufficient fee to miners will take longer to process or fail altogether.

Jeff Garzik’s previous proposal to address this contentious issue, BIP 100, seeks to implement a shifting limit determined by miners, who would vote on the limit every 3 months. As it allows for market feedback, this option is likely preferable to any arbitrary size increase and, at least until the historical cap of 32 MB is reached, should prevent this divisive issue from arising again in the near future.


Gavin Andresen, Mike Hearn and others have also put forward suggestions but as of yet none has reached a clear consensus among developers, miners, businesses or the community. Garzik’s BIP 102 is thus a stopgap measure, aimed at keeping blocks from becoming full without making too radical a change, until a permanent solution meets with more unanimamous support. Despite being a relatively modest proposal, BIP 102 has not met with anything like universal support, not least because it implies enduring two hard forks rather than one.

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