What is blockchain in simple words
A blockchain is a shared record of transactions that many computers keep at the same time. New records are grouped into blocks, and each block contains a fingerprint of the previous one, so old entries cannot be changed without everyone noticing. That simple idea is what lets Bitcoin, TON and other networks work without a bank in the middle. Here it is in plain words, with a live example.
Blockchain in simple words
Imagine a notebook that thousands of people hold identical copies of. Every few minutes someone proposes a new page of entries. Everyone checks the page against the rules, and if it is valid, they all add it to their copy. Nobody can quietly tear out an old page, because every page also carries a fingerprint of the page before it, and thousands of other copies would disagree.
That notebook is the blockchain, the pages are blocks, and the fingerprint is a hash.
What is inside a block
- Transactions: who sent how much to whom.
- The hash of the previous block: the link that makes it a chain.
- A timestamp.
- Proof that the block was made by the rules: in Bitcoin, a number called a nonce that makes the block's hash small enough.
Why the chain cannot be rewritten
A hash function such as SHA-256 turns any data into a short fingerprint. Change one character and the fingerprint changes completely. If someone edits an old transaction, that block's hash changes, which breaks the link stored in the next block, and the next, all the way to today. To hide the edit, the attacker would have to redo every block after it faster than the rest of the network, which on a large network is practically impossible.
Try it yourself
Type anything and change one letter: the SHA-256 fingerprint changes completely. This is the same function Bitcoin uses to link blocks.
SHA-256 of this text
More hash functions, including MD5 and SHA-512, are in our online hash tool.
Who decides which block is next
Thousands of independent computers need a fair way to agree on the next block. The two main methods:
| Method | How it works | Used by |
|---|---|---|
| Proof of work | Miners race to find a hash below a target; the winner adds the block and gets a reward | Bitcoin, Litecoin |
| Proof of stake | Validators lock coins as a deposit and take turns proposing blocks; cheating costs them the deposit | Ethereum, TON |
Proof of work is what people call mining. How it works step by step: what is crypto mining.
What blockchains are used for
- Digital money: Bitcoin, TON's coin GRAM and stablecoins like USD₮ that track the dollar.
- Payments across borders without a bank between the sender and the receiver.
- Ownership records: NFTs, including Telegram usernames and collectible gifts on TON.
- Transparent history: every transfer can be checked in a block explorer by its hash.
Smart contracts
A smart contract is a small program stored on the blockchain that runs exactly as written. "If payment arrives, send the token" happens automatically, with no company in the middle. Wallets, exchanges, games and NFT markets on Ethereum and TON are built from smart contracts.
Limits and myths
- "Blockchain is anonymous." Usually not: every transaction is public, only names are hidden behind addresses.
- "Data on a blockchain is always true." The chain only proves nobody changed the record later. If wrong data was entered, it stays wrong.
- "Blockchain makes any project safe." Scams can run on blockchains too. The technology does not check whether a project is honest.
You can see a blockchain-style network in action in TotalHash, a free mining game in Telegram: your phone computes SHA-256 hashes to close blocks, the same kind of work Bitcoin miners do.
Watch your phone close blocks in a Telegram mining game.
Open TotalHashQuick answers
What is blockchain in simple terms?
A shared record of transactions kept by many computers at once. Records are grouped into blocks, and each block contains the hash of the previous one, so history cannot be changed unnoticed.
How does blockchain technology work?
Participants check each new block against the rules, add it to their copy, and link it to the previous block with a hash. A consensus method such as proof of work or proof of stake decides who adds the next block.
What is a blockchain wallet?
An app that holds the keys to your addresses on a blockchain and lets you send and receive coins. The coins themselves stay recorded on the blockchain.
Is blockchain the same as Bitcoin?
No. Bitcoin is one cryptocurrency that runs on its own blockchain. Blockchains are also used by Ethereum, TON and many other networks.
What are smart contracts?
Programs stored on a blockchain that run exactly as written, for example sending a token automatically when a payment arrives.