Bitcoin Mining Pool Centralization and Block-Template Authority
How concentrated is Bitcoin mining? Nakamoto coefficient, HHI and per-pool hashrate share across time windows.
Quick answer
Over the last month, Bitcoin's hashrate was spread across 18 identified mining pools, but it takes only 3 pools to control more than half the network — the Nakamoto coefficient. The HHI concentration index is 1,435 (unconcentrated), and the single largest pool mined 24.9% of blocks. Lower Nakamoto and higher HHI both mean more centralization.
Solo and decentralized-template mining (DATUM, Stratum V2 job declaration) push the Nakamoto coefficient up and template sovereignty with it. Full data — every window, free to download under CC BY 4.0.
Template sovereignty: who actually builds the block?
Hashrate share tells you who finds blocks — not who decides what goes in them. On most pools the operator builds the block template and the miner only supplies proof-of-work, so the operator chooses which transactions confirm. Over the last month just 4.32% of Bitcoin's hashrate mined on a pool that lets the miner build its own block template: OCEAN (2.62%), Braiins Pool (1.7%) — via Stratum V2 job declaration, OCEAN's DATUM, or a self-hostable / peer-to-peer pool. On the other 94.56% of identified hashrate the pool operator builds the template and picks the transactions.
Capability footprint, not confirmed adoption. This is the share of hashrate on pools that permit miner-built templates, not blocks proven to use it. On P2Pool, Public Pool and self-hosted pools that is the default; on Braiins Pool and OCEAN it is opt-in (Stratum V2 job declaration and DATUM) and still lightly adopted, so the share of blocks the miner actually built is smaller — under about 1% today. It also cannot see self-hosted solo miners, who are unattributable (~1.12% “unknown”). Read 4.32% as the addressable ceiling on today's pools, not the achieved figure. Live shares from mempool.space, as of 2026-09-06.
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Centralization is not one number
Pool-attributed block share measures coordination, but it does not identify every control plane. Two systems with the same visible share can assign template, payout, and infrastructure authority differently.
| Control plane | Question | Evidence | What pool share cannot prove |
|---|---|---|---|
| Hashrate coordination | How much observed work is attributed to one coordinator? | Dated block attribution, window, and unknown bucket | Who selected every transaction |
| Block templates | Who chooses transactions, coinbase structure, and permitted mutations? | Protocol trace, implementation, and reproducible fixture | Whether an advertised option is deployed |
| Share accounting | Who validates shares and keeps worker balances or statistics? | Server behavior and reconciliation tests | Who controls final settlement |
| Reward/custody | Where does a found block pay and can an intermediary delay or redirect it? | Decoded coinbase, payout policy, and on-chain settlement | Whether miners chose the template |
| Infrastructure | Which DNS, hosting, network, and operator dependencies can interrupt work? | Architecture and independent failure tests | Administrative independence from a brand |
What “solo” changes
Solo mining describes the reward outcome. It does not, by itself, identify who built the template, receives the coinbase, operates the node, or controls the Stratum endpoint. Ask who constructs work, where the coinbase pays, which software validates shares, and whether the path can be reproduced.
Where Stratum V2 fits
Job Declaration and Template Distribution separate protocol roles, but specifications are capabilities—not deployment evidence. Verify a named service with a dated trace, negotiated messages, implementation evidence, and a reproducible custom-job test.
Primary references: BIP 22, BIP 23, the Bitcoin Core mining RPC, and the Stratum V2 Job Declaration and Template Distribution specifications.
Continue with own-node solo infrastructure, pool payout schemes, the Stratum reference, and the evidence-led solo-service comparison.
Concentration by time window
| Window | Pools | Nakamoto | HHI | Top pool | Top 3 |
|---|---|---|---|---|---|
| Last week | 17 | 3 | 1,458 | 26.8% | 59% |
| Last month | 18 | 3 | 1,435 | 24.9% | 59% |
| Last 3 months | 25 | 3 | 1,445 | 25.4% | 58.9% |
| Last year | 32 | 3 | 1,526 | 28.6% | 58.6% |
Current pool shares (last month)
| # | Pool | Blocks | Share |
|---|---|---|---|
| 1 | Foundry USA | 1109 | 24.86% |
| 2 | AntPool | 844 | 18.92% |
| 3 | F2Pool | 679 | 15.22% |
| 4 | SpiderPool | 418 | 9.37% |
| 5 | ViaBTC | 360 | 8.07% |
| 6 | MARA Pool | 215 | 4.82% |
| 7 | SECPOOL | 194 | 4.35% |
| 8 | Luxor | 166 | 3.72% |
| 9 | OCEAN | 117 | 2.62% |
| 10 | Binance Pool | 91 | 2.04% |
| 11 | Braiins Pool | 76 | 1.7% |
| 12 | BTC.com | 65 | 1.46% |
| 13 | Unknown | 50 | 1.12% |
| 14 | NiceHash | 48 | 1.08% |
| 15 | Poolin | 15 | 0.34% |
| 16 | WhitePool | 11 | 0.25% |
| 17 | ULTIMUSPOOL | 2 | 0.04% |
| 18 | Mining-Dutch | 1 | 0.02% |
Method: The Nakamoto coefficient is the fewest pools whose combined share exceeds 50% of blocks — the smaller it is, the easier a majority coalition. HHI sums the squared percentage shares (US DOJ guide: <1500 unconcentrated, 1500-2500 moderate, >2500 highly concentrated). Pool attribution from mempool.space is a proxy based on coinbase tags (see which tag each pool stamps). See also the mining-pool database.
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Last reviewed June 18, 2026.