All terms
A shared record of transactions that no single party controls.
A blockchain is a list of transactions, grouped into blocks, where each block carries a fingerprint of the one before it. Change anything in an old block and every fingerprint after it breaks, which is what makes the history tamper evident.
Thousands of computers keep their own copy and agree on which block comes next. There is no central database and no administrator who can quietly edit a row. That is the whole trick, and everything else in crypto is built on top of it.
When you send Bitcoin, your transaction joins a block roughly every ten minutes. Once six more blocks sit on top of it, reversing it would mean redoing all that work.
That the coins live on the blockchain and the wallet holds them. The blockchain is only a record of who owns what. Your wallet holds the key that lets you change that record, which is why losing the key loses the coins even though the record still says they are yours.
Common questions
Is a blockchain the same as a database?
Are all blockchains public?
Where this comes up on the site
The guides that actually use this word, rather than a list of everything we have written.
Where to go next
More foundations terms
Want this explained out loud?
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