Block Size War: Everything to Know

By  Beluga Research August 29, 2023

Image for Block Size War: Everything to Know


  • The cryptocurrency block size war refers to the contentious debate within the crypto community regarding the optimal size of blocks in a blockchain
  • The block size issue arose when Bitcoin's creator limited the block size to 1MB, causing scalability issues
  • The war intensified in 2017, resulting in a fork which the created Bitcoin Cash (BCH) with an 8MB block size
  • Bitcoin implemented SegWit as a compromise solution to increase transaction capacity while maintaining decentralization


The cryptocurrency block size war refers to the contentious debate within the crypto community regarding the optimal size of blocks in a blockchain, impacting transaction speed and scalability.

Blockchain technology, the foundation of cryptocurrencies like Bitcoin, relies on a decentralized network of nodes to validate and record transactions. Each transaction is grouped into blocks, which are then added to the blockchain. The block size refers to the maximum amount of data that a block can contain. The debate surrounding the block size centers on finding the optimal balance between scalability, security and decentralization.

A Brief History

The block size war can be traced back to 2010 when Bitcoin's creator, Satoshi Nakamoto, set a maximum block size of 1MB. This limit was initially meant to prevent spam attacks and ensure a smooth functioning of the network. However, as Bitcoin gained popularity, it became evident that the 1MB block size was inhibiting scalability, causing delays and increased transaction fees.

The Bitcoin community continued to focus on developing and implementing various scalability solutions beyond the block size debate. The Lightning Network, a second-layer solution built on top of Bitcoin, gained traction as a way to facilitate fast and low-cost transactions by leveraging payment channels.

The original Bitcoin blockchain continued to maintain the 1 MB block size limit. The community's focus shifted towards layer 2 solutions and other improvements to enhance scalability without sacrificing decentralization.

What is the Block Size War?

The block size war intensified in 2017 when the Bitcoin community became divided over how to address scalability issuse. One camp argued for increasing the block size, while the other advocated for off-chain solutions like the Lightning Network. This disagreement led to the hard fork that resulted in the creation of Bitcoin Cash (BCH) in August 2017.

Bitcoin Cash, with its larger block size of 8MB, aimed to provide faster and cheaper transactions. Proponents of Bitcoin Cash argued that larger blocks would enable more transactions per second and improve scalability. On the other hand, supporters of Bitcoin (BTC) believed that increasing the block size would compromise decentralization and make it more difficult for regular users to run full nodes.

While Bitcoin Cash gained some traction, Bitcoin remained the dominant cryptocurrency. The block size debate continued within the Bitcoin community, with proposals like Segregated Witness (SegWit) emerging as a compromise solution. SegWit aimed to increase transaction capacity by separating transaction signature data from the block, effectively increasing the block size limit without a hard fork.

Ultimately, SegWit was implemented on the Bitcoin network in August 2017 as a soft fork. This allowed for a gradual adoption by users and minimized the risk of a contentious split. SegWit successfully increased transaction capacity and reduced fees, but it did not completely resolve the block size war.

Getting Started

To understand the block size war, it's essential to grasp the basics of how a blockchain operates. A blockchain is a decentralized ledger that records all transactions made within a cryptocurrency network. Transactions are grouped into blocks, which are then added to the chain in a sequential manner. Each block contains a set number of transactions and is linked to the previous block, forming the blockchain.

The block size directly impacts the scalability and transaction capacity of a blockchain. A larger block size allows more transactions to be processed within a given time frame, potentially improving the network's throughput. However, larger blocks also require more storage space and processing power, making it more challenging for individual network participants to validate and propagate blocks.

Unique Aspects

The block size debate gained prominence as Bitcoin's popularity surged, which led to increased network congestion and transaction fees. Some members of the Bitcoin community argued that the block size limit of 1 megabyte (MB) was stifling the network's growth and inhibiting its ability to handle a higher volume of transactions. They proposed increasing the block size to accommodate more transactions per block, thus reducing congestion and lowering fees.

On the other side of the debate were those who advocated for retaining the 1 MB block size limit. They argued that increasing the block size would introduce centralization risks, as fewer participants would have the resources to validate and store larger blocks. They believed that maintaining a smaller block size would ensure a more decentralized and secure network.

The disagreement escalated into a contentious and prolonged debate, with both sides presenting technical arguments, economic considerations and philosophical viewpoints. Various proposals were put forth, including Bitcoin Classic, Bitcoin Unlimited and Segregated Witness (SegWit).

Bitcoin Classic proposed a straightforward increase in the block size to 2 MB, aiming to improve transaction throughput. Bitcoin Unlimited, on the other hand, advocated for a dynamically adjustable block size, allowing the network to scale according to demand. SegWit, with a different approach, sought to optimize block space utilization by segregating transaction signature data, essentially increasing the effective block capacity without altering the block size limit.

The block size war created divisions within the Bitcoin community, leading to heated discussions, online debates, and even the emergence of rival cryptocurrency projects. Some supporters of larger blocks forked Bitcoin's codebase to create alternative cryptocurrencies, such as Bitcoin Cash, which increased the block size to 8 MB, and Bitcoin SV, which aimed for an even larger block size of 128 MB.


  • Increased Transaction Throughput: A larger block size allows for more transactions to be included in each block, leading to higher throughput and faster confirmation times.
  • Enhanced Scalability: With larger block sizes, a blockchain network can handle a greater volume of transactions, accommodating increased user adoption and preventing congestion.
  • Lower Transaction Fees: When blocks have more space for transactions, the competition for inclusion decreases, resulting in lower transaction fees for users.
  • Improved User Experience: Faster confirmation times and lower fees can enhance the overall user experience, making cryptocurrencies more practical for everyday transactions.
  • Incentives for Miners: Larger blocks can potentially provide miners with more transaction fees and block rewards, incentivizing their participation in securing the network.
  • Network Resilience: A blockchain network with larger block sizes may be more resistant to spam attacks, as the cost of flooding the network with transactions increases, becoming more prohibitive.


  • Centralization Pressures: Larger block sizes require more storage and bandwidth resources, making it challenging for individual users to participate as full nodes. This can lead to increased centralization, as only entities with sufficient resources can effectively validate and store the entire blockchain, thereby limiting widespread participation.
  • Network Bottlenecks: Larger blocks take longer to propagate through the network, potentially causing bottlenecks and delays in block confirmation. This can hinder the overall efficiency of the blockchain network.
  • Increased Storage Requirements: As block sizes grow, the storage requirements for running a full node also increase significantly. This can limit the number of participants who can afford to store the entire blockchain, potentially compromising the decentralization of the network.
  • Security Risks: Larger blocks increase the complexity of validating transactions, potentially introducing security vulnerabilities and increasing the risk of consensus failures or network splits.
  • Bandwidth Limitations: Nodes with limited bandwidth may struggle to keep up with the increased data flow from larger block sizes, leading to synchronization issues and potential network fragmentation.
  • Potential for Blockchain Bloat: A blockchain with larger block sizes can grow rapidly, consuming more storage space and making it more challenging for new participants to join the network.