Bitcoin is a software-based online payment system described by Satoshi Nakamoto[note 1] in 2008[5] and introduced as open-source software in 2009.[6] Payments are recorded in a public ledger using its own unit of account,[7] which is also called bitcoin.[note 2] Payments work peer-to-peer without a central repository or single administrator, which has led the US Treasury to call bitcoin a decentralized virtual currency.[11] Although its status as a currency is disputed, media reports often refer to bitcoin as a cryptocurrency or digital currency.[12] Bitcoin is the first fully implemented decentralized cryptocurrency; most other cryptocurrencies are similar and derived from it. It is also the largest cryptocurrency by market capitalization.[13]
