bitcoin
Bitcoin is the first decentralized digital currency, created in 2009 by the pseudonymous Satoshi Nakamoto. It runs on a global network with no central authority, has a fixed supply of 21 million coins, and is secured by the proof-of-work mechanism.
Bitcoin is a peer-to-peer electronic cash system described in a 2008 whitepaper by a person or group using the pseudonym Satoshi Nakamoto. The Bitcoin network launched in January 2009, when Nakamoto mined the first block, known as the Genesis Block. Unlike every previous attempt at digital money, Bitcoin solved the double-spend problem without requiring a trusted third party. It does this through a distributed ledger called the blockchain, maintained by a global network of nodes and secured by the proof-of-work mechanism known as mining.
Bitcoin has a fixed maximum supply of 21 million coins, written directly into the protocol. No authority can change that number. New bitcoin enters circulation only through mining, at a rate that decreases over time through scheduled events called halvings. The smallest unit of bitcoin is the satoshi, equal to one hundred millionths of a bitcoin (0.00000001 BTC). Bitcoin can be divided and sent in fractions, making it practical across a wide range of transaction sizes.
Bitcoin operates without a central point of control. No company owns it, no government issues it, and no single developer can change its rules. Modifications to the protocol require broad consensus among node operators, miners, and the wider community. Bitcoin was designed to be resistant to censorship, seizure, and arbitrary rule changes. It is an open network that anyone can access, use, or build on without requiring permission from anyone.