Bitcoin
Commonly used logo of bitcoin | |
| Denominations | |
|---|---|
| Plural | bitcoins |
| Symbol | ₿ (Unicode: U+20BF ₿ BITCOIN SIGN) |
| Code | BTC |
| Precision | 10−8 |
| Subunits | |
| 1⁄1000 | millibitcoin |
| 1⁄1000000 | microbitcoin |
| 1⁄100000000 | satoshi |
| Development | |
| Original author | Satoshi Nakamoto |
| White paper | "Bitcoin: A Peer-to-Peer Electronic Cash System" |
| Implementation | Bitcoin Core |
| Initial release | 0.1.0 / 9 January 2009 |
| Latest release | 30.2.0 / 10 January 2026 |
| Code repository | github |
| Development status | Active |
| Written in | C++ |
| Source model | Free and open-source software |
| License | MIT License |
| Ledger | |
| Ledger start | 3 January 2009 |
| Timestamping scheme | Proof of work (partial hash inversion) |
| Hash function | SHA-256 (two rounds) |
| Issuance schedule | Decentralized (block reward) Initially ₿50 per block, halved every 210,000 blocks |
| Block reward | ₿3.125 (as of 2025) |
| Block time | 10 minutes |
| Circulating supply | ₿19,934,271 (as of 14 October 2025) |
| Supply limit | ₿21,000,000 |
| Valuation | |
| Exchange rate | Floating |
| Website | |
| Website | bitcoin |
Bitcoin (abbreviation: BTC; sign: ₿) is the first decentralized cryptocurrency. Based on a free-market ideology, bitcoin was invented in 2008 when an unknown person published a white paper under the pseudonym of Satoshi Nakamoto. Use of bitcoin as a currency began in 2009, with the release of its open-source implementation. From 2021 to 2025, El Salvador adopted it as legal tender currency before revoking it. As bitcoin is pseudonymous, its use by criminals has attracted the attention of regulators, leading to its ban by several countries.
Bitcoin works through the collaboration of computers, each of which acts as a node in the peer-to-peer bitcoin network. Each node maintains an independent copy of a public distributed ledger of transactions, called a blockchain, without central oversight. Transactions are validated through the use of cryptography, preventing one person from spending another person's bitcoin, as long as the owner of the bitcoin keeps certain sensitive data secret.
Consensus between nodes about the content of the blockchain is achieved using a computationally intensive process based on proof of work, called mining, which is performed by purpose-built computers. Mining consumes large quantities of electricity and has been criticized for its environmental impact.