Mining Centralization

Mining centralization is the concern that Bitcoin's hash rate is concentrated in too few hands, undermining the decentralization property Bitcoin depends on.

The structural reality in 2026:

• A few mining pools coordinate most of the hash rate. Over the year to mid-October 2026, Foundry USA, AntPool, F2Pool and ViaBTC mined about 69% of all blocks between them.
• A few ASIC manufacturers supply most of the hardware. Cambridge's 2025 industry survey put Bitmain at 82% of the ASIC market, MicroBT at 15% and Canaan at 2%.
• A few jurisdictions host most of the mining. The US is the largest: 75% of the hash rate reported by the 49 firms in Cambridge's 2025 survey, a sample Cambridge says may overstate the US. China's 2021 ban shifted geography substantially; in September 2019 Cambridge's mining map had put 75.5% of global hash rate in China.

What this means in practice:

• A coordinated attack is theoretically possible. Pools collectively controlling >50% of hash rate could attempt to reorg recent blocks, censor specific transactions, or double-spend their own outputs. None of this has happened at scale on Bitcoin, but the capability exists.
• A single point of pressure exists. Governments wanting to censor Bitcoin transactions could in principle pressure mining pool operators in their jurisdictions to comply. This has been observed in milder forms: in late 2023 F2Pool was caught leaving transactions that spent from an OFAC-sanctioned address out of its blocks, a co-founder confirmed it, and the pool said it would stop for now.

What counterbalances it:

• Pools aren't miners. The hash rate inside a pool comes from individual miners who can point their machines at a different pool at any time. A pool caught misbehaving hands every one of them a reason to leave.
• Stratum V2 progress. The new pool-miner protocol's Job Declaration lets miners build their own block templates, leaving the pool to account shares and pay out. Adoption is gradual but moving in the right direction.
• Geographic dispersion has improved. Compared to 2019, when about three-quarters of hash rate sat in China, the network is spread across more countries, even if the US now holds a large share of its own.
• Mining hardware is fungible. Miners can and do route their hash rate through different pools, in different jurisdictions, on short notice.

The honest assessment: mining centralization is a real concern with real failure modes, but the structural counterweights are also real. It's an area worth watching, worth pushing back on with Stratum V2 adoption and pool-operator scrutiny, and worth not panicking about. See Mining rabbit hole section 8 for a longer look.

For a night when one pool operator could decide which of two chains survived, and what that says in both directions, see The 2013 Chain Fork.