Block Weight

Block weight is a metric used in Bitcoin to define the limits of a block's size, expressed in "weight units." Since the SegWit upgrade, each block can have up to 4 million weight units—roughly equal to 4 megabytes (MB) of data. This limit controls how many transactions fit into a single block and helps keep the blockchain manageable, ensuring that individuals can still run their own nodes and independently verify the network. Before SegWit, block limits were set to 1MB by size alone. The move to weight units balances regular and SegWit transactions, making the system more flexible while still supporting Bitcoin’s decentralization.