Block Size

Block size is a protocol-level rule that caps how much transaction data a single block can hold, and it directly shapes how many transactions a blockchain can process and how expensive that space becomes. A hard limit forces transactions to compete for a scarce resource: when demand rises, users bid higher fees to get included sooner, while a generous limit keeps fees low but raises the cost of running a full node.

Bitcoin's original 1MB cap, set by Satoshi Nakamoto in 2010, became a bottleneck as adoption grew, eventually causing multi-hour confirmation delays and fees spiking to tens of dollars per transaction in 2017. Rather than raising the raw byte limit, Bitcoin adopted Segregated Witness (SegWit), which restructured how transaction data is counted and pushed the effective ceiling toward roughly 4MB of "block weight." A rival camp instead forked the chain to create Bitcoin Cash, which launched with an 8MB limit and later raised it to 32MB to favor cheap, high-volume payments over node-operating simplicity.

Other networks make different tradeoffs: some raise the cap outright, others keep blocks small but shorten block time, and Ethereum avoids a fixed byte limit entirely by capping resource usage per block with a gas limit instead. Bigger blocks generally increase Transactions Per Second (TPS) capacity, but they also grow the blockchain's total storage footprint and can discourage participants from running independent nodes, a core tension in blockchain scaling design.