Bitcoin (BTC)

Bitcoin (BTC) is the first cryptocurrency and the native asset of the Bitcoin network. It is a digital bearer asset with no issuer: new coins are created by a fixed schedule written into the protocol, and ownership is proven by control of a private key rather than by an account at a bank. Bitcoin can be sent directly between users anywhere in the world, without a central operator approving the payment.

The word "Bitcoin" is used for two things. This entry covers the coin: its supply, uses, market and regulation. The network that records and secures it is described in Bitcoin Blockchain. Bitcoin is usually compared with gold and with fiat currency, and every other cryptocurrency is, by convention, an altcoin.

Imagine a notebook that lists who owns every bitcoin, with an identical copy kept by thousands of strangers around the world. To pay someone, you announce "move one coin from my line to theirs" and sign the request with a secret password that only you know. Everyone checks that the signature is real and that you actually own the coin, then writes the change into their copy. Nobody can quietly scribble in an extra coin, because everyone else's copy would disagree.

New coins are "dug up" a little like gold: computers compete to solve a puzzle, and the winner receives fresh bitcoins as a prize. The prize shrinks on a fixed timetable, so the total can never pass 21 million. Like cash in a wallet, whoever controls the secret password owns the coins. Lose it, and there is no bank to call.

A paper titled "Bitcoin: A Peer-to-Peer Electronic Cash System" was published on 31 October 2008 under the name Satoshi Nakamoto, whose identity has never been confirmed. The network started on 3 January 2009, when the first block was mined. The first widely cited commercial purchase came on 22 May 2010, when a programmer in Florida paid 10,000 BTC for two pizzas, a date now marked by enthusiasts as "Bitcoin Pizza Day".

Early trading took place on small exchanges, the largest of which, Mt. Gox in Tokyo, collapsed in 2014 after losing customer coins. Since then Bitcoin has moved from a niche experiment to an asset held by funds, listed companies and some governments. In January 2024 the US Securities and Exchange Commission approved the first spot Bitcoin exchange-traded funds, which began trading on 11 January 2024.

Bitcoin's supply is capped at just under 21 million coins. New coins enter circulation as a reward to miners for each block they add under proof of work. The reward started at 50 BTC and halves every 210,000 blocks, roughly every four years. Adding up every halving period gives the cap:

• $S$ is the total number of bitcoins that will ever be issued.
• $i$ is the halving period, counting from 0 for the first 210,000 blocks.
• $\frac{50}{2^{i}}$ is the block reward in that period, in BTC.

For example, after the fourth halving in April 2024 the period number is 4, so the reward is $50 \div 2^{4} = 3.125$ BTC per block. At about 144 blocks a day, that is roughly 450 new bitcoins a day. Because rewards are rounded down to whole satoshis (one hundred-millionth of a bitcoin), the final total is slightly below 21 million, and the last new coins are expected around the year 2140.

• Savings and investment. Many holders treat Bitcoin as a store of value because its supply cannot be increased by a central bank, a view held most strongly by the Bitcoin maximalist community.
• Payments and transfers. Bitcoin is used for cross-border payments and remittances, and small, fast payments are often sent over the Lightning Network.
• Treasury reserves. Some listed companies hold Bitcoin on their balance sheets, and in March 2025 a US executive order created a Strategic Bitcoin Reserve from coins the government already held.
• Legal tender. El Salvador made Bitcoin legal tender in September 2021, then amended the law in January 2025 so that businesses are no longer required to accept it.

Bitcoin trades around the clock on centralized exchanges, over-the-counter desks, peer-to-peer platforms and kiosks such as the Bitcoin ATM. It has had the largest market capitalization of any cryptocurrency since it began trading, and its price has been far more volatile than that of major currencies or gold: falls of 50 percent or more within a year have happened several times, most recently in 2022. Prices are quoted for a whole coin, but most purchases are for a fraction of one, since a bitcoin divides into 100 million satoshis. Holders either leave coins with a custodian or keep the keys themselves, often in a cold wallet that is kept offline.

Bitcoin itself is not issued by any company, so regulators focus on the businesses around it. In the United States the Commodity Futures Trading Commission treats it as a commodity, the IRS treats it as property for tax purposes, and exchanges must follow money-transmission and anti-money-laundering rules. Elsewhere, service providers fall under rules such as MiCA in the European Union and the FATF Travel Rule. The main risks are price swings, loss or theft of keys, exchange failures, and the energy used by mining. Lost keys cannot be recovered, and confirmed transactions cannot be reversed.

• Bitcoin: A Peer-to-Peer Electronic Cash System (original white paper)
• Bitcoin Core
• Ask Mint: Is Bitcoin better understood as a payment network, a currency, or both?