A mining pool is a group of cryptocurrency miners who combine their computing power to solve blocks more frequently, then share the rewards proportionally based on each miner's contribution.
Solo mining Bitcoin today is statistically equivalent to buying one lottery ticket against millions of competitors. The expected time for a solo miner with 100 TH/s (a modern ASIC) to find a Bitcoin block is over 10 years. Mining pools solve this by combining hash power — turning a rare jackpot into a predictable income stream.
When the pool finds a block, the 3.125 BTC reward is split among all participants based on the share of hash power each contributed. Instead of waiting years for a single payout, miners receive small, consistent payments — sometimes daily.
Mining pools charge 1-3% of earnings for coordination. Payment models differ: PPS (Pay Per Share) pays you for every valid share submitted regardless of block luck — predictable income, higher fees. PPLNS (Pay Per Last N Shares) rewards loyalty and recent contributions — lower fees but more variance. FPPS (Full Pay Per Share) includes transaction fee revenue in the share calculation — currently the most popular model for Bitcoin.
Size: larger pools mean more frequent but smaller payouts. Smaller pools offer bigger but rarer payouts. Fee structure: compare total effective cost, not just stated fee. Payout threshold: how much you need before receiving payment — important for small miners. Server location: closer servers reduce latency and rejected shares. Reputation: look for pools that have operated without issues for years.
The largest Bitcoin pools by hash rate: Foundry USA (~30%), AntPool (~20%), F2Pool (~12%), ViaBTC (~10%).
A growing concern: if any entity controls 51%+ of Bitcoin's total hash rate, they could theoretically reorganize the blockchain — double-spend transactions, censor blocks. This is the 51% attack. Currently, no single pool controls this much, but the top 3 pools together often exceed 51% — raising questions about coordination risk.