By 2025, Bitcoin mining has become noticeably more centralized than ever before. According to research by independent analyst b10c, the six largest pools control more than 95% of the blocks mined. This concentration of computing power can become a threat to the stability and decentralization of the network.
In the Bitcoin mining industry, all of the hashrate is controlled by a few large pools. These pools decide which transactions to include or exclude from their blocks. This situation does not undermine Bitcoin’s censorship resistance as long as the pools do not collude to block transactions or attack the network. But how many independent mining pools are there, really?
A 51% attack, in which a pool (or several colluding pools) controls more than half of the hashrate and can build its own blockchain, is well known. However, even with only 40% of the hashrate, a pool has about a 50% chance of mining six consecutive blocks.
What are the threats to the network from dominant pools?
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prevent other miners from finding blocks (selfish mining)
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fork the main blockchain, dividing the network into two competing chains in order to double-spend coins and steal money from service providers, exchanges, and money changers (double-spending)
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not skip or confirm certain transactions or blocks (censoring)
Are there any pools with this level of hashrate today? And in general, how centralized is Bitcoin mining today? Especially considering the supposed proxy mining, in which small pools do work on behalf of larger pools, while indicating their name in the coinbase transaction.
How is centralization measured?
Hashrate distribution is analyzed using coinbase transactions—special information added by pools to each block. These records allow you to determine which pool mined a specific block. The calculations were made using a 31-day rolling average of the number of blocks mined by each pool.
As of 2025, based on mining data from apirone, the top five mining pools are as follows:
- Foundry — 30%
- AntPool — 19%
- ViaBTC — 14.5%
- F2Pool — 10%
- MARA Pool — 5%
To assess the level of mining centralization, you can calculate the Mining centralization index, an indicator that reflects the share of the hashrate controlled by the 2, 3, 4, 5, and 6 largest pools. The higher the index values, the higher the level of centralization.
Centralization index
In May 2017, the share of the two largest pools was less than 30%, and the six were less than 65%. This was the peak of decentralization in the history of Bitcoin mining. In December 2023, these figures were over 55% and 90%, respectively. Compared to 2019–2022, when the top 2 accounted for about 35% and the top 6 accounted for about 75%, mining has become much more centralized in 2025.
Proxy mining and the role of AntPool
Note the hidden centralization caused by so-called proxy mining. A number of small pools, including several affiliated with AntPool, use other people’s block templates but substitute their own names in coinbase transactions. This understates the real share of AntPool, which, together with “friendly” pools — the notional “AntPool & Co.” group — could control up to 40% of the network hashrate in 2023–2024.
Updated calculations show that over the past two years, the AntPool & Co. group and Foundry have collectively held 60-70% of the network's computing power. Moreover, 96-99% of blocks were mined by just six pools. These numbers indicate that Bitcoin mining is heavily centralized around a few pools that produce templates.
The threat of transaction and block censorship
In addition to breaking the blockchain trilemma (security, decentralization, and scalability), transactions and blocks can be censored, which would completely break the idea of the blockchain. Already, various KYC analysts have different attitudes towards transactions. For example, payments from Russian exchanges can be blocked on American ones. The same can happen with cryptocurrency on sanctioned wallets. Yes, the Bitcoin protocol does not allow you to block funds, as happened with USDT of the Garantex exchange. But just imagine what will happen if miners are forced not to include “unwanted” transactions or recipients in a block. Censoring Bitcoin at the miner level would immediately undermine trust in the protocol.
What's next? The alternative is small pools and home mining
Small pools such as SlushPool (2%), SBI Crypto (<1%), Ocean (<1%), and Demand (<1%) are very important, as well as powerful solo miners. If you follow crypto news, you can see how they find blocks and receive a reward for the entire block and a fee for transactions in it. Although the share of home mining today is still insignificant in the overall hashrate. In addition, small companies with high power could start independent mining, leaving large pools.
Are there pools with 40% of the hashrate today?
No, but as of mid-2025, Foundry has a hashrate of 30 to 35. Currently, AntPool and Foundry have over 51% of the hashrate combined.
How Centralized Is Bitcoin Mining Today?
According to the Mining centralization index, Bitcoin mining was most decentralized for a short period in May 2017. 2019-2022 was also a good period. Since 2023 onwards, Bitcoin mining is becoming increasingly centralized, especially with large pools like Foundry and proxy pooling a la AntPool.
