What is Bitcoin?

By the Blockhorizon Editorial Team · Updated 2 October 2026 · How we check facts

Where did Bitcoin come from?

Bitcoin started as a nine-page paper titled “Bitcoin: A Peer-to-Peer Electronic Cash System”, written under the name Satoshi Nakamoto. The PDF itself carries no date; the US National Institute of Standards and Technology (NIST) places it in 2008 and says the Bitcoin network itself went live in 2009.

NIST also notes that Bitcoin is what made blockchain technology widely known: it was the first of the many cryptocurrencies that followed. The mechanics below come from that original paper and NIST’s technical overview; the risks come from financial regulators — not from anyone selling Bitcoin.

What problem was Bitcoin designed to solve?

The paper’s goal is simple: let one person pay another online without going through a financial institution.

The hard part is a problem called double-spending. Digital money is just data, and data can be copied. If I send you a digital coin, how do you know I haven’t already sent the same coin to someone else? Normally a trusted middleman — a bank, or what the paper calls a “mint” — checks every payment. The paper’s objection is that the whole money system then depends on whoever runs that middleman.

Bitcoin’s answer is to make the full history of payments public, and to have many independent computers agree on a single version of that history.

How does Bitcoin work, step by step?

The whitepaper describes the network in a few steps:

1. Broadcast. A new payment is announced to all participating computers (called nodes).
2. Collect. Each node gathers new payments into a candidate block.
3. Work. Nodes compete to solve a difficult computing puzzle for their block (the “proof-of-work”, explained below).
4. Announce. The first node to solve it broadcasts its block to the network.
5. Check. Other nodes accept the block only if every payment in it is valid and none of the coins has already been spent.
6. Build on it. Nodes show they accept the block by starting work on the next one, which includes a reference to it.

Each block points back to the one before it, so the blocks form a chain — the blockchain. When versions disagree, the paper says nodes treat the longest chain — the one with the most work behind it — as the valid one.

What is proof-of-work and why does it matter?

Proof-of-work is the puzzle in step 3. A node repeatedly changes a number in its block (the nonce) and runs the block through a hash function (Bitcoin uses SHA-256) until the result starts with a required number of zero bits. There is no shortcut: the only way to find a valid answer is to keep guessing, which costs computing power and electricity.

That cost is the point. Once a block has been “worked”, changing anything inside it would mean redoing its work — and the work of every block added after it. The paper calculates that an attacker with less computing power than the honest network falls further behind with every new block. For example, it works out that an attacker controlling 10% of the network’s computing power has roughly a 0.09% chance of catching up from five blocks behind.

According to NIST, Bitcoin adjusts the puzzle’s difficulty every 2,016 blocks so that, on average, one new block appears about every ten minutes.

How are new bitcoins created?

Under the whitepaper’s design, the first transaction in each new block creates new coins and pays them to whoever produced that block. Any transaction fees in the block are added to that reward. This is the incentive for people to spend money on the computing work that secures the network.

The whitepaper itself never states a maximum number of coins — it only says that once “a predetermined number of coins” have entered circulation, rewards can shift entirely to fees. The number comes from the software. In Bitcoin Core, the reference software, the reward started at 50 BTC per block and halves every 210,000 blocks (the code comments say roughly every four years). Added up, that schedule issues just under 21 million BTC — about 20,999,999.98 by exact arithmetic on the code’s rules. The Federal Reserve Bank of St. Louis notes that no central bank controls this supply.

Is Bitcoin anonymous?

Not fully. Every transaction is announced publicly, and anyone can see that an amount moved from one address to another. The privacy in the whitepaper’s design comes from keeping the owners of those addresses unnamed — the paper compares it to a stock exchange publishing trades without saying who made them. If an address is ever linked to you, your history on the public ledger can be traced.

Where is your Bitcoin actually stored?

Bitcoin is not a file on your phone. Ownership is recorded on the shared ledger, and what you hold is a private key — a secret number that lets you move the coins linked to it. NIST and the US Securities and Exchange Commission (SEC) both warn that a lost private key cannot be regenerated or replaced, so the coins it controls are lost for good. Our guide to crypto wallets and private keys covers this in detail.

What are the risks of owning Bitcoin?

Regulators in the UK, EU and US are unusually direct about crypto risk:

• Price swings. The UK Financial Conduct Authority (FCA) says crypto is high-risk and speculative. Its own example: Bitcoin peaked at £93,947 on 6 October 2025 and was £65,350 on 1 December 2025 — a fall of 30.44% in under two months.
• You could lose everything you put in. The FCA says you should be prepared to lose all your money; EU supervisors say prices “can fall and rise quickly” and you may lose “a lot, or even all” of what you invest.
• Little protection. The FCA says it is highly unlikely you would be covered by the UK’s compensation scheme, and EU supervisors say you will not benefit from compensation schemes even under the EU’s MiCA rules.
• Key and platform risk. Lose your keys and the coins are gone; leave them with a platform and you take on its hacks, failures or bankruptcy (SEC).
• Scams. Fraudsters use Bitcoin’s popularity to sell fake platforms and “guaranteed” returns. Learn the red flags of crypto scams before you buy anything.

Blockhorizon is an education site. Nothing here is a recommendation to buy, sell or hold Bitcoin or any other crypto-asset.