What is Bitcoin?
The first cryptocurrency, why it matters, and what you're actually buying when you buy it.
Bitcoin is the first cryptocurrency: digital money with no company or government in charge, launched in 2009. Its rules cap the supply at 21 million coins, transactions are recorded on a public blockchain, and new blocks are added by miners using proof of work.
Where it came from
In October 2008, during the financial crisis, someone using the name Satoshi Nakamoto published a nine-page paper, "Bitcoin: A Peer-to-Peer Electronic Cash System." The network went live in January 2009. Satoshi's real identity is still unknown, and they stopped communicating publicly around 2011.
The breakthrough was solving the "double-spend" problem: making sure the same digital coin can't be spent twice, without trusting a bank to keep score.
Why there will only ever be 21 million
New bitcoins are created as a reward for miners who add blocks. That reward is cut in half about every four years (every 210,000 blocks), an event called the halving. It started at 50 bitcoins per block in 2009 and has been 3.125 since the April 2024 halving. The next is expected around 2028.
| Period | New bitcoins per block |
|---|---|
| 2009–2012 | 50 |
| 2012–2016 | 25 |
| 2016–2020 | 12.5 |
| 2020–2024 | 6.25 |
| 2024–about 2028 | 3.125 |
Because the reward keeps halving, the total approaches 21 million and stops. The 20 millionth bitcoin was mined in March 2026; the last fraction of a coin is expected around the year 2140. A few million coins are believed to be lost forever in wallets whose keys are gone.
You don't have to buy a whole bitcoin
One bitcoin divides into 100,000,000 satoshis ("sats"). You can buy $10 or $20 worth. Use the unit converter to switch between BTC and sats.
How it works
- Mining: computers compete to add the next block by doing a huge amount of guessing work. That's proof of work. It uses a lot of electricity, and that cost is what makes rewriting history so expensive.
- Blocks every ~10 minutes: the network adjusts the difficulty every 2,016 blocks (about two weeks) to keep that pace.
- Public ledger: every transaction ever made is visible. Addresses aren't names, but they're not anonymous either; they can often be traced.
Why people buy it
Supporters see it as "digital gold": scarce, hard to seize or inflate, and usable anywhere. Since January 2024, people in the US can also buy it through spot Bitcoin ETFs at an ordinary brokerage. Critics point to its volatility, energy use, and the fact that it produces no income. Both sides are worth understanding.
Bitcoin's price has fallen more than 70% from its peak several times, including in 2011, 2014–15, 2018 and 2022. Nobody can tell you where it goes next.
Check what you learned
3 quick questions. Answers stay on your device.
Frequently asked questions
Who owns Bitcoin?
No one owns the network. Anyone can run the software, and changing its rules needs broad agreement from the people running it.
Can Bitcoin be hacked?
The Bitcoin network itself has never been successfully hacked to steal coins. Exchanges, apps and individual wallets have been, which is why how you store it matters.
What is a halving?
Every 210,000 blocks, about every four years, the number of new bitcoins paid to miners for each block is cut in half. The last was in April 2024, from 6.25 to 3.125.
How many bitcoins are left to mine?
Fewer than 1 million. The 20 millionth was mined in March 2026, and the remainder will be released more and more slowly until about 2140.
Where to next
Sources
- Bitcoin: A Peer-to-Peer Electronic Cash System
- How Bitcoin works (bitcoin.org)
- Bitcoin's mined supply hits 20 million (The Block, March 2026)
- Satoshi (unit), Bitcoin Wiki
Written for beginners and checked against the sources listed. Last reviewed October 26, 2026. This page is educational and is not financial, tax or legal advice. How we write and check pages.