Bitcoin is the world's first cryptocurrency, a form of electronic cash. It is the first decentralized digital currency: the system works without a central bank or single administrator. Bitcoins are sent from user to user on the peer-to-peer bitcoin network directly, without the need for intermediaries. 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 and released as open-source software in 2009.

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.Bitcoin

Denominations
Plural bitcoins
Symbol ₿[a]
Ticker symbol BTC, XBT[b]
Subunits
 ​1⁄1000 millibitcoin
 ​1⁄100000000 satoshi[2]
Coins Unspent outputs of transactions (in multiples of a satoshi)[3]:ch. 5
Development
Original author(s) Satoshi Nakamoto
White paper "Bitcoin: A Peer-to-Peer Electronic Cash System"[4]
Implementation(s) Bitcoin Core
Initial release 0.1.0 / 9 January 2009 (9 years ago)
Latest release 0.16.1 / 15 June 2018 (10 days ago)
Website bitcoin.org
Ledger
Ledger start 3 January 2009 (9 years ago)
Timestamping scheme Proof-of-work (partial hash inversion)
Hash function SHA-256
Issuance Decentralized (block reward)[6][7]
Block reward ₿12.5[c]
Block time 10 minutes
Block explorer blockchain.info
Circulating supply ₿16,858,762 (as of 11 February 2018)
Supply limit ₿21,000,000 [5]
The symbol was encoded in Unicode version 10.0 at position U+20BF ₿ BITCOIN SIGN in the Currency Symbols block in June 2017.[1]
Compatible with ISO 4217.
July 2016 to approximately June 2020, halved approximately every four years