---
bip: 102
title: "Block size increase to 2MB"
status: Closed
type: Specification
layer: "Consensus (hard fork)"
authors: ["Jeff Garzik"]
assigned: 2015-06-23
last_modified: 2025-10-08
topics: ["capacity","blocks"]
url: https://bipexplorer.com/bip/102
source: https://github.com/bitcoin/bips/blob/master/bip-0102.mediawiki
---

# BIP 102: Block size increase to 2MB

> **In plain English:** Proposed a single, simple increase in the maximum block size from 1 MB to 2 MB to allow more transactions per block. Being a change that older software would reject, it would have required a hard fork, and it was one of the competing options in the block size debate.

## Abstract

Simple, one-time increase in total amount of transaction data permitted in a block from 1MB to 2MB.

## Motivation

1.  Continue current economic policy.

1.  Exercise hard fork network upgrade.

## Specification

1.  MAX\_BLOCK\_SIZE increased to 2,000,000 bytes at trigger point.

1.  Increase maximum block sigops by similar factor, preserving SIZE/50 formula.

1.  Trigger: (1) Block time 00:00:00 on flag day, AND (2) 95% of the last 1,000 blocks have signaled support.

## Backward compatibility

Fully validating older clients are not compatible with this change. The first block exceeding 1,000,000 bytes will partition older clients off the new network.

## Discussion

In the short term, an increase is needed to continue to current economic policies with regards to fees and block space, matching market expectations and preventing market disruption.

In the long term, this limit should focus on reflecting the maximum network engineering limit.

## Implementation

[https://github.com/jgarzik/bitcoin/tree/2015\_2mb\_blocksize](https://github.com/jgarzik/bitcoin/tree/2015_2mb_blocksize)