A data driven analysis of the bitcoin block size, revealing how growth was partially constrained by miner policy and Bitcoin Core defaults.

Welcome to the latest mempool research report. In this report, we'll be looking at how the size of bitcoin blocks changed over time. We explore how block size changed following the SegWit upgrade and see how the bitcoin blockchain is expected to grow in the coming years.

Executive Summary

This report examines Bitcoin block size evolution from the network's inception through February 2025. Our analysis reveals that the commonly assumed narrative of block size growth being constrained solely by the 1 MB consensus limit is incomplete. Rather, Bitcoin Core configuration defaults and miner selected configuration values played a significant role in constraining block sizes, frequently constraining them below the level of transaction demand.

We then analyse how block size has changed following SegWit and how from January 2023 to February 2025 we have seen a high block space utilization driven by both a persistent transaction backlog and the emergence of inscription protocols, which has resulted in a notable increase in the growth rate of the blockchain.

We also present a novel and reproducible approach to identify transaction backlogs / mempool clearing events, and project how block chain size will change over the coming years.

...read more at research.mempool.space