TL;DR
Bitcoin is the first decentralized cryptocurrency, launched in 2009, with a hard supply cap of 21 million coins. The network produces a block every ~10 minutes, and the block reward halves every 210,000 blocks (~4 years): after the 4th halving in April 2024 it is 3.125 BTC, with the 5th expected around 2028 (1.5625 BTC). Consensus is proof of work (PoW).
Core mechanics
| Mechanism | Detail |
|---|---|
| Ledger | Public blockchain maintained by full nodes |
| Consensus | PoW: miners race to find a valid hash |
| Blocks | ~10 minutes each, difficulty auto-adjusts |
| Supply | 21M cap enforced by halvings |
| Keys | Private key signs transactions; loss = permanent loss |
| Confirmations | 6 confirmations (~1 hour) is the common safety threshold |
Halving timeline
| Event | Date | Block reward |
|---|---|---|
| Genesis | 2009-01 | 50 BTC |
| 1st halving | 2012-11 | 25 BTC |
| 2nd halving | 2016-07 | 12.5 BTC |
| 3rd halving | 2020-05 | 6.25 BTC |
| 4th halving | 2024-04 | 3.125 BTC |
| 5th (expected) | ~2028 | 1.5625 BTC |
FAQ
How are bitcoins created?
By mining: miners package transactions and find a hash below the difficulty target to earn block rewards plus fees; rewards halve every 210,000 blocks.
How is the 21M cap enforced?
The halving schedule is hard-coded, pushing rewards toward zero (~2140). A version changing the cap would not be accepted by consensus.
Can I recover a lost private key?
No. Bitcoin is "keys = ownership"; there is no customer service. Back up seed phrases/private keys offline.
Sources
- bitcoin.org (getting started), accessed 2026-08-04
- Bitcoin whitepaper (Satoshi Nakamoto, 2008), accessed 2026-08-04
- blockchain.com halving data, accessed 2026-08-04