Bitcoin is the world's first cryptocurrency, a form of electronic cash.[8]:3[9] It is the first decentralized digital currency: the system was designed to work without a central bank or single administrator.[8]:1[10] Bitcoins are sent from user to user on the peer-to-peer bitcoin network directly, without the need for intermediaries.[8]:4,5 These transactions are verified by network nodes through cryptography and recorded in a public distributed ledger called a blockchain. Bitcoin was invented by an unknown person or group of people using the name Satoshi Nakamoto[11] and released as open-source software in 2009.[12]
Bitcoins are created as a reward for a process known as mining. They can be exchanged for other currencies,[13] products, and services. Research produced by the University of Cambridge estimates that in 2017, there were 2.9 to 5.8 million unique users using a cryptocurrency wallet, most of them using bitcoin.
Many economists and investors consider the bitcoin market to be a bubble. Bitcoin has also been criticized for its use in illegal transactions, its high electricity consumption, price volatility, and thefts from exchanges.