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Bitcoin (abbreviation: BTC; sign: ₿) is the first decentralized cryptocurrency.

Based on a free-market ideology, bitcoin was invented in 2008 when an unknown person published a white paper under the pseudonym of Satoshi Nakamoto. Use of bitcoin as a currency began in 2009, with the release of its open-source implementation. From 2021 to 2025, El Salvador adopted it as legal tender currency before revoking it. As bitcoin is pseudonymous, its use by criminals has attracted the attention of regulators, leading to its ban by several countries. Bitcoin works through the collaboration of computers, each of which acts as a node in the peer-to-peer bitcoin network. Each node maintains an independent copy of a public distributed ledger of transactions, called a blockchain, without central oversight. Transactions are validated through the use of cryptography, preventing one person from spending another person's bitcoin, as long as the owner of the bitcoin keeps certain sensitive data secret. Consensus between nodes about the content of the blockchain is achieved using a computationally intensive process based on proof of work, called mining, which is performed by purpose-built computers. Mining consumes large quantities of electricity, with surveyed miners reporting that 52% of their electricity use came from sustainable energy sources, and has been criticized for its environmental impact.

On 31 October 2008, a link to a white paper authored by Satoshi Nakamoto titled Bitcoin: A Peer-to-Peer Electronic Cash System was posted to a cryptography mailing list. On May 22, 2010, the first known commercial transaction using bitcoin occurred when programmer Laszlo Hanyecz bought two Papa John's pizzas for ₿10,000, in what would later be celebrated as "Bitcoin Pizza Day". Satoshi tasked Finnish developer and early Bitcoin contributor Martti Malmi with creating content for the bitcoin.org website. In March 2013, the US Financial Crimes Enforcement Network (FinCEN) established regulatory guidelines for "decentralized virtual currencies" such as bitcoin, classifying American bitcoin miners who sell their generated bitcoins as money services businesses, subject to registration and other legal obligations. SegWit opponents, who supported larger blocks as a scalability solution, forked to create Bitcoin Cash, one of many forks of bitcoin. In January 2024, the first 11 US spot bitcoin ETFs began trading, offering direct exposure to bitcoin for the first time on American stock exchanges. As of 2025, the Salvadoran government continues to describe Bitcoin as legal tender under the 2021 Bitcoin Law; however, a January 2025 reform removed obligations for businesses and the government to accept it, so many analysts regard its legal-tender status as effectively ended in practice.

The unit of account of the bitcoin system is the bitcoin. No uniform capitalization convention exists; some sources use Bitcoin, capitalized, to refer to the technology and network, and bitcoin, lowercase, for the unit of account. Units for smaller amounts of bitcoin are the millibitcoin (mBTC), equal to 1⁄1000 bitcoin, and the satoshi (sat), representing 1⁄100000000 (one hundred millionth) bitcoin, the smallest amount possible.

As a decentralized system, bitcoin operates without a central authority or single administrator, so that anyone can create a new bitcoin address and transact without needing any approval. This process tracks bitcoin spending, ensuring each bitcoin is spent only once.

In the bitcoin network, each bitcoin is treated equally, ensuring basic fungibility.

Forks of Bitcoin Core exist such as Bitcoin Unlimited.

From September 2021 until January 2025, the Bitcoin Law made bitcoin a legal tender currency in El Salvador, alongside the US dollar. El Salvador still describes bitcoin as "legal tender", but its acceptance is no longer obligitory (as it is with the US dollar) and the El Salvador government no longer accepts bitcoin for payment of taxes or fees. Since 2020, Iran has required local bitcoin miners to sell bitcoin to the Central Bank of Iran, allowing the central bank to use it for imports.

Quick Facts

• Bitcoin works through the collaboration of computers, each of which acts as a node in the peer-to-peer bitcoin network.
• Transactions are validated through the use of cryptography, preventing one person from spending another person's bitcoin, as long as the owner of the bitcoin keeps certain sensitive data secret.
• From September 2021 until January 2025, the Bitcoin Law made bitcoin a legal tender currency in El Salvador, alongside the US dollar.
• Use of bitcoin as a currency began in 2009, with the release of its open-source implementation.
• As bitcoin is pseudonymous, its use by criminals has attracted the attention of regulators, leading to its ban by several countries.

Source material: Wikipedia - "Bitcoin". Adapted and summarized for DiscoverScroll. Original contributors are credited through the linked Wikipedia article. Read original on Wikipedia. CC BY-SA 4.0. Changes were made from the original.