Bitcoin () is a decentralized digital currency, without a central bank or single administrator, that can be sent from user to user on the peer-to-peer bitcoin network without the need for intermediaries.[7] Transactions are verified by network nodes through cryptography and recorded in a public distributed ledger called a blockchain. The cryptocurrency was invented in 2008 by an unknown person or group of people using the name Satoshi Nakamoto.[8] The currency began use in 2009[9] when its implementation was released as open-source software.[6]:ch. 1

Bitcoin
Prevailing bitcoin logo
Prevailing bitcoin logo
Denominations
Pluralbitcoins
Symbol₿ (Unicode: U+20BF  BITCOIN SIGN (HTML ₿))[a]
Ticker symbolBTC, XBT[b]
Precision10−8
Subunits
11000millibitcoin
1100000000satoshi[2]
Development
Original author(s)Satoshi Nakamoto
White paper"Bitcoin: A Peer-to-Peer Electronic Cash System"[4]
Implementation(s)Bitcoin Core
Initial release0.1.0 / 9 January 2009 (12 years ago)
Latest release0.21.1 / 2 May 2021 (48 days ago)[3]
Code repositoryhttps://github.com/bitcoin/bitcoin
Development statusActive
Websitebitcoin.org
Ledger
Ledger start3 January 2009 (12 years ago)
Timestamping schemeProof-of-work (partial hash inversion)
Hash functionSHA-256
Issuance scheduleDecentralized (block reward)
Initially ₿50 per block, halved every 210,000 blocks[7]
Block reward₿6.25[c]
Block time10 minutes
Block explorerMany implementations
Circulating supply₿18,660,000 (as of 20 March 2021)
Supply limit₿21,000,000[5][d]