Blockchain
Also called: distributed ledger · chain
Definition
A blockchain is a shared digital ledger, copied across many computers, where transactions are grouped into blocks that are linked in order and are extremely hard to change after the fact.
This entry is shown in English.
How Blockchain works
Each block holds a batch of transactions plus a cryptographic fingerprint (a hash) of the block before it. Because every block points back to the previous one, changing an old transaction would change its hash and break every block after it. Thousands of independent computers, called nodes, keep their own copy and reject a version that does not follow the rules.
New blocks are added through a consensus mechanism. Bitcoin uses proof of work, where miners spend electricity to compete for the right to add the next block. Ethereum and many newer networks use proof of stake, where validators lock up coins as collateral. Either way, no single company decides which transactions are valid.
For you as a user, the blockchain is the public record of who owns what. When you withdraw coins from an exchange, the transfer is final once it is recorded and confirmed on-chain. There is no customer service desk that can reverse it, which is why sending to the wrong address or the wrong network usually means the funds are lost.
Example
Suppose you send 0.05 BTC from an exchange to your own wallet. The exchange broadcasts the transaction, and it waits in a queue until a miner includes it in a block, roughly every 10 minutes on Bitcoin. After that block is added, your transfer has 1 confirmation. Many exchanges wait for 2 to 6 confirmations before crediting a Bitcoin deposit, so the money can take 20 to 60 minutes to appear, even though anyone can already see it on a block explorer.
Common mistakes
- Assuming a blockchain transfer can be cancelled or refunded like a card payment once it is confirmed.
- Thinking every blockchain is the same network, then sending tokens on one chain to an address on an unsupported chain.
- Believing that data on a blockchain is automatically true, when it only proves what was recorded, not whether a project is honest.
Learn and practise
FAQ
Is a blockchain the same as Bitcoin?
No. Bitcoin is one cryptocurrency that runs on its own blockchain. Ethereum, Solana and many other networks each run their own separate blockchains.
Can a blockchain be hacked?
Large public blockchains like Bitcoin and Ethereum have never had their core ledger rewritten in a normal way, because that would require controlling a huge share of mining or stake. Most losses come from hacked exchanges, buggy smart contracts or stolen private keys, not from the chain itself.
Who controls a public blockchain?
No single party. The rules are enforced by the software that thousands of independent nodes run, and changes need broad agreement from developers, node operators and miners or validators.