How Bitcoin Works

Miners compete to solve cryptographic puzzles, creating a cost barrier to attacks. Current hashrate (680 EH/s) requires ~$3.2B daily hardware investment to control 51% of the network. This economic burden makes reversing confirmed transactions infeasible. Historical data shows zero successful 51% attacks on Bitcoin's mainnet since 2009.

Fees function as a Stackelberg competition where transactions bid for block space. Median fees range 15-45 sat/vB based on mempool demand. Miners prioritize higher-fee transactions during congestion. Lightning Network users bypass on-chain fees entirely, settling batched transactions with sub-satoshi costs for most use cases.

The protocol enforces a programmatic schedule: halving block rewards every 210,000 blocks (~4 years). Current supply approaches theoretical maximum through diminishing issuance. This fixed scarcity contrasts fiat money expansion. As of October 2026, circulating supply stands at 21.38M BTC with final satoshis entering circulation by 2140.

Lightning enables off-chain payment channels, theoretically supporting millions of TPS. Current capacity exceeds 8,000 BTC across 80,000+ active channels (Q3 2026). Users can transact instantly with microsatoshi-level fees. However, liquidity provisioning and capital efficiency remain technical considerations for widespread adoption.

Centralization of mining hashrate remains the structural concern—three pools currently control ~51% of hashrate as of October 2026, though pools distribute reward sovereignty among miners. Protocol-level risks are minimal: network upgrades require consensus, and soft-fork activation requires overwhelming node support. Long-term energy cost trends could compress miner margins.