Block Size
The maximum amount of data a single blockchain block is permitted to contain, which directly limits how many transactions can be processed per block.
Block size is the maximum amount of data, typically measured in megabytes, that a single block on a blockchain is permitted to contain. Because each transaction takes up a certain amount of data, block size directly caps how many transactions a single block can hold, which in turn affects the network's overall transaction throughput and, during periods of high demand, how much competition exists for the limited space in each block's transaction fee market (see Kaavon's "Transaction Fee Market" glossary definition).
Bitcoin's block size specifically became the subject of an intense, multi-year community dispute known as the "block size wars," between those favoring larger blocks to directly increase transaction throughput and lower fees, and those favoring keeping blocks smaller to preserve lower hardware requirements for running a full node (see Kaavon's "Full Node" glossary definition), reasoning that larger blocks would make running a full node more resource-intensive and could push the network toward greater centralization among fewer, better-resourced node operators. That dispute was a significant contributing factor behind Bitcoin's 2017 hard fork that created Bitcoin Cash.
Examples
- A larger block size allows more transactions per block, but also increases the storage and bandwidth requirements for anyone running a full node to keep up with the chain.
- Bitcoin's prolonged block size debate, over whether to increase throughput or keep node requirements low, was a major contributing factor behind the 2017 hard fork that created Bitcoin Cash.