A free course in how Bitcoin works
How Bitcoin works, in 6 levels
Short lessons in plain words that answer the questions people actually ask about Bitcoin. Most show live figures from the chain.
- 45 lessons
- 6 levels
- about 3½ hours
Pick up where you left off
1.1What Bitcoin is0 of 45 lessons read
How each lesson works
- ReadA few minutes in plain words, starting with the questions the lesson answers.
- See it on the chainLive figures from the chain, stamped with the block they come from.
- Check yourselfA few questions to think through before you reveal the answers.
- Go onEach lesson leads to the next, with its sources and the date it was last checked.
The levels
6 levels, in order. Start at Level 1, or go straight to the question you came with.
Level 1
Bitcoin basics
For anyone curious. Start here.
- 1.1What Bitcoin is4 minA shared record of payments that anyone can check. We start from the newest block.
- 1.2Who runs Bitcoin?5 minNo company, no CEO. Who keeps it going, and whether anyone can shut it down.
- 1.3How many bitcoin there are4 min21 million at most. How many exist today, and when the next halving comes.
- 1.4What a satoshi is3 minThe smallest unit, and why nobody needs to buy a whole bitcoin.
- 1.5Why bitcoin has value5 minNothing backs it, yet people pay for it. What they are paying for.
- 1.6Why the price moves so much5 minA fixed supply meets changing demand. Why a day can bring 5% either way.
- 1.7Who created Bitcoin4 minSatoshi Nakamoto, the white paper and the first year, from the record itself.
- 1.8Bitcoin, crypto and blockchain4 minHow Bitcoin differs from the thousands of coins that came after it.
Level 2
How it works
What happens under the hood, without the maths.
- 2.1Keys, addresses and wallets4 minAn address receives. A wallet holds the keys and uses many addresses.
- 2.2How a payment works4 minFollow the first payment between two people, from Satoshi to Hal Finney in block 170.
- 2.3Fees and confirmations4 minWhat a payment costs right now, and what confirmed means.
- 2.4How mining works5 minWhy miners spend electricity, what difficulty is, and what they are paid.
- 2.5Nodes: who checks the rules5 minThe computers that refuse bad blocks, and why anyone can run one.
- 2.6Can Bitcoin be hacked?5 minWhat has been hacked over the years, and what hasn't.
- 2.7Lightning: fast small payments5 minHow payments can settle in seconds and still rest on the chain.
Level 3
Getting, keeping and spending
For when you own some bitcoin, or are about to.
- 3.1Before your first bitcoin5 minWhere to start, and the mistakes beginners make most often.
- 3.2Wallets: where bitcoin is kept5 minApps, hardware devices and exchange accounts: what each one really holds.
- 3.3On an exchange or in your own wallet5 minWho holds the keys, and what happened when exchanges failed.
- 3.4Seed phrases and backups5 minThe words that restore a wallet, and how people lose them.
- 3.5How buying bitcoin works5 minExchanges, apps and ATMs: the steps, the fees and the checks.
- 3.6Sending and receiving5 minThe address, the amount, the fee, and why a test payment helps.
- 3.7Did my payment arrive?5 minPending, stuck or sent to the wrong address: what each one means.
- 3.8Selling and cashing out4 minHow bitcoin turns back into money in a bank account.
- 3.9Spending bitcoin4 minPaying with bitcoin in practice, on the chain and with Lightning.
- 3.10Taxes and records5 minWhy selling or spending can be taxed, and which records help.
- 3.11If something happens to you5 minHow bitcoin passes to family, and how it gets lost instead.
Level 4
Staying safe
The scams that cost people the most, and how to spot them.
- 4.1Rules that catch most scams4 minA few plain rules that help you spot a scam.
- 4.2The common scams6 minGiveaways, fake platforms, romance and job scams, told from real cases.
- 4.3Someone asked me to pay in bitcoin4 minBitcoin ATMs, "government" calls and urgent payments: what to do.
- 4.4Fake apps, fake support5 minHow seed phrases are stolen, and the look-alike address trick.
- 4.5If you've been scammed5 minWhat can and can't be done, and the recovery scam that follows.
Level 5
Reading the chain
For looking at addresses and payments yourself.
- 5.1What a block explorer shows5 minReading a transaction and an address, field by field.
- 5.2What 1, 3, bc1q and bc1p mean5 minFour kinds of address, how they differ, and what they don't reveal.
- 5.3Pieces, change and balances5 minUnspent outputs, change, dust, and why a balance can show zero.
- 5.4What the chain shows about you5 minAddress reuse, linking, and what anyone can see.
- 5.5Who holds bitcoin5 minExchanges, funds, companies and governments, by the addresses they publish.
- 5.6Lost and sleeping coins4 minHow many bitcoin have not moved in years, and what that can and can't tell us.
Level 6
Bitcoin and the world
The bigger questions people argue about.
- 6.1Bitcoin's energy use6 minHow much electricity mining uses, and the main arguments on both sides.
- 6.2Is bitcoin legal?4 minHow rules differ by country, and what usually applies.
- 6.3Funds, companies and governments5 minETFs, company treasuries and state holdings, and what they change.
- 6.4When the last bitcoin is mined4 minWhat pays miners once new coins stop, around 2140.
- 6.5Quantum computers and Bitcoin5 minWhat the risk is, which coins it touches, and what is being done.
- 6.6Forks and upgrades8 minHow Bitcoin changes, and what happened when people disagreed.
- 6.7History you can check5 minThe pizza, Mt. Gox, Silk Road and the Bitfinex hack, on the chain.
- 6.8Proving a file existed4 minTimestamping a document on Bitcoin.
About Learn
Where do the figures come from?
From a Bitcoin node, which keeps a full copy of the chain and checks every block. Prices come from a public market feed. Each lesson lists its sources.
Who writes the lessons?
The team behind satoshis.watch. We correct lessons when something changes and show the date each was last checked.