Bitcoin[a] (₿) is a cryptocurrency invented in 2008 by an unknown person or group of people using the name Satoshi Nakamoto and started in 2009 when its implementation was released as open-source software.:ch. 1
BitcoinPrevailing bitcoin logoDenominationsPluralbitcoinsSymbol₿ (Unicode: U+20BF ₿ BITCOIN SIGN (HTML
₿))[a]Ticker symbolBTC, XBT[b]Precision10−8Subunits 1⁄1000millibitcoin 1⁄100000000satoshiDevelopmentOriginal author(s)Satoshi NakamotoWhite paper"Bitcoin: A Peer-to-Peer Electronic Cash System"Implementation(s)Bitcoin CoreInitial release0.1.0 / 9 January 2009 (11 years ago)Latest release0.20.1 / 2 August 2020 (27 days ago)Development statusActiveWebsitebitcoin.orgLedgerLedger start3 January 2009 (11 years ago)Timestamping schemeProof-of-work (partial hash inversion)Hash functionSHA-256Issuance scheduleDecentralized (block reward)
Initially ₿50 per block, halved every 210,000 blocksBlock reward₿6.25[c]Block time10 minutesBlock explorerwww.blockchain.com/explorerCirculating supply₿18,355,100 (as of 1 May 2020)Supply limit₿21,000,000[d]
^ The symbol was encoded in Unicode version 10.0 at position U+20BF ₿ BITCOIN SIGN in the Currency Symbols block in June 2017.
^ Compatible with ISO 4217.
^ May 2020 to approximately 2024, halved approximately every four years
^ The supply will approach, but never reach, ₿21 million. Issuance will permanently halt c. 2140 at ₿20,999,999.9769.:ch. 8
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It 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. Transactions are verified by network nodes through cryptography and recorded in a public distributed ledger called a blockchain. Bitcoins are created as a reward for a process known as mining. They can be exchanged for other currencies, products, and services. Research produced by 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 has been praised and criticized. Critics noted its use in illegal transactions, the large amount of electricity used by miners, price volatility, and thefts from exchanges. Some economists, including several Nobel laureates, have characterized it as a speculative bubble. Bitcoin has also been used as an investment, although several regulatory agencies have issued investor alerts about bitcoin.