Bitcoin (BTC)
The first cryptocurrency, reduced to the facts that matter: who launched it, how its fixed issuance schedule works and what can go wrong for a holder.
On this page
- Bitcoin's genesis block is dated 3 January 2009,[4] and its design comes from a white paper signed Satoshi Nakamoto.[1]
- Only 21 million bitcoins will ever be created; one bitcoin divides into 100,000,000 satoshis.[2]
- New BTC enters circulation as a block subsidy that halves every 210,000 blocks, roughly every four years.[4]
- Transactions cannot be reversed, and lost keys mean lost coins: no company can recover them.[2]
- In March 2026 the SEC named bitcoin as an example of a digital commodity, not a security.[9]
What is Bitcoin and who created it?
Bitcoin is a payment network run by independent computers, and BTC (bitcoin) is the currency that moves on it. Its design was published in a white paper titled Bitcoin: A Peer-to-Peer Electronic Cash System, signed Satoshi Nakamoto.[1] The paper's goal was electronic cash sent directly from one party to another without a financial institution in the middle.[1]
According to bitcoin.org, Nakamoto published the first specification and proof of concept on a cryptography mailing list in 2009 and left the project in late 2010 without revealing much about himself.[2] Nobody owns the network, much as nobody owns the technology behind email.[2] Our explainer What is Bitcoin? covers the concept; this page is the fact sheet.
How does the Bitcoin network work?
Nodes collect new transactions into blocks. Miners compete to find a proof-of-work: a value that makes the block's SHA-256 hash start with enough zero bits.[1] The first valid block is broadcast, other nodes check that its transactions are valid and unspent, and then build the next block on top of it.[1]
The protocol targets one block about every 10 minutes.[4] Every 2,016 blocks, the network compares how long those blocks actually took with the two-week ideal and raises or lowers the mining difficulty.[5] The developer guide notes that reliably rewriting confirmed history would take a majority of the network's hash power, an attack known as a 51% attack.[5] For the hardware side, see how Bitcoin mining works.
How are new bitcoins created?
Each block's first transaction pays the miner a block subsidy plus the fees of the transactions in that block.[5] In Bitcoin Core, the reference software, the subsidy started at 50 BTC and is cut in half every 210,000 blocks, which the code comment says happens approximately every four years.[4] Our halving explainer shows the full schedule.
| Subsidy era | Starts at block | BTC per block | Total issued by end of era |
|---|---|---|---|
| 1st | 0 | 50 | 10.5 million |
| 2nd | 210,000 | 25 | 15.75 million |
| 3rd | 420,000 | 12.5 | 18.375 million |
| 4th | 630,000 | 6.25 | 19.6875 million |
| 5th (current) | 840,000 | 3.125 | 20.34375 million |
Totals are our calculation from the Bitcoin Core subsidy rule.[4] Added up across every era, the subsidies come to slightly under 21 million BTC, and the subsidy reaches zero at block 6,930,000.[4]
What is bitcoin used for?
The original purpose is direct online payment between two parties.[1] Payments are settled on-chain, and bitcoin.org suggests waiting for more confirmations, around six, before treating a high-value transfer as settled.[3]
Two later developments widened how BTC is used. The Lightning Network paper describes payment channels in which two parties exchange signed but unbroadcast transactions off-chain and settle on Bitcoin later.[7] BIP 141, the SegWit proposal, describes its fix for transaction malleability as important for off-chain protocols such as Lightning.[6] See the Lightning Network explained.
Bitcoin is also held through regulated products. In January 2024 the SEC approved the listing of a number of spot bitcoin exchange-traded products, while Chair Gensler stressed that the agency did not approve or endorse bitcoin itself.[8] More in spot bitcoin ETFs explained.
What are the key dates in Bitcoin's history?
Dates below come from Bitcoin Core's code, bitcoin.org, the original proposals and US regulators. Calendar dates of the four halvings are not given in the primary sources we checked, so the table above lists them by block height.
| Date | Event |
|---|---|
| 3 January 2009 | Genesis block timestamped 18:15:05 UTC in Bitcoin Core's chain parameters[4] |
| 2009 | First specification and proof of concept posted to a cryptography mailing list[2] |
| Late 2010 | Satoshi Nakamoto leaves the project[2] |
| 21 December 2015 | BIP 141 (Segregated Witness) created[6] |
| 14 January 2016 | Lightning Network paper, draft v0.5.9.2[7] |
| 10 January 2024 | SEC approves spot bitcoin exchange-traded products[8] |
| 17 March 2026 | SEC interpretive release names BTC as an example of a digital commodity[9] |
What are the specific risks of holding bitcoin?
- Price swings. bitcoin.org itself warns that the price can rise or fall unpredictably over short periods and tells users not to store money they cannot afford to lose.[3]
- No undo button. A confirmed transaction cannot be reversed; only the recipient can send a refund.[2]
- Key loss. Coins whose private keys are lost stay dormant forever.[2] With self-custody, the SEC notes you may permanently lose access if a wallet is lost, stolen or hacked; with a custodian, you carry the risk of its hack or bankruptcy.[10]
- Public history. Every transaction is stored publicly and permanently, so Bitcoin is not anonymous.[3]
- Rules differ by country. Most jurisdictions have not banned bitcoin, but some restrict or ban its use.[2]
What mistakes do beginners make with bitcoin?
- Treating one confirmation as final for a large payment. bitcoin.org suggests six confirmations as a good minimum for high-value transfers.[3]
- Storing the seed phrase online. The SEC advises keeping it secure and never sharing it.[10] See seed phrases explained.
- Expecting a company to fix mistakes. No one owns the network, so no help desk can reverse a payment.[2]
- Confusing BTC with look-alike tokens. Check which network and asset you are actually buying or receiving.
Questions readers ask
Who is Satoshi Nakamoto?
The name signed on the Bitcoin white paper.[1] bitcoin.org says Nakamoto left the project in late 2010 without revealing much about himself, and the identity remains unconfirmed.[2]
Will there ever be more than 21 million bitcoins?
Not under the current rules. bitcoin.org states that only 21 million will ever be created,[2] and the subsidy schedule in Bitcoin Core adds up to slightly less.[4] Changing that would require a change to the consensus rules that nodes run.
Can I buy part of a bitcoin?
Yes. One bitcoin is 100,000,000 satoshis, so amounts down to 0.00000001 BTC are possible.[2]
Is bitcoin a security in the US?
The SEC's March 2026 interpretive release, joined by the CFTC, lists BTC as an example of a digital commodity.[9] See SEC vs CFTC for who regulates what.
Bitcoin is a proof-of-work network whose currency follows a published schedule: a subsidy that halves every 210,000 blocks toward a cap just under 21 million.[4] What it does not have is a company that can reverse payments, restore lost keys or steady the price. Check how you will store it before you decide to hold any.
Sources
- Satoshi Nakamoto (bitcoin.org), Bitcoin: A Peer-to-Peer Electronic Cash System (2008)Primary source
- bitcoin.org, Frequently Asked Questions (2024)Primary source
- bitcoin.org, Some things you need to know (2024)Primary source
- Bitcoin Core, Bitcoin Core source: GetBlockSubsidy (validation.cpp) and mainnet chain parameters (2026)Primary source
- Bitcoin Project (developer.bitcoin.org), Bitcoin Developer Guide: Block Chain (2024)Primary source
- Bitcoin Improvement Proposals, BIP 141: Segregated Witness (Consensus layer) (2015)Primary source
- Joseph Poon and Thaddeus Dryja, The Bitcoin Lightning Network: Scalable Off-Chain Instant Payments (2016)Primary source
- US Securities and Exchange Commission, Statement on the Approval of Spot Bitcoin Exchange-Traded Products (2024)Primary source
- US Securities and Exchange Commission, SEC Clarifies the Application of Federal Securities Laws to Crypto Assets (2026-30) (2026)Primary source
- US Securities and Exchange Commission (Investor.gov), Crypto Asset Custody Basics for Retail Investors (2025)Primary source
Educational content only — not financial, investment, legal or tax advice. Crypto-assets are high-risk and you could lose all the money you put in. Rules differ by country; check with your national regulator. See our risk disclosure and editorial policy.
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