How blockchain works

Blockchain is a decentralized digital ledger that securely records transactions across a network of computers without needing a central authority like a bank.

It works as a continuous chain of blocks. Each block contains:

- A batch of transactions (e.g., cryptocurrency transfers, smart contract executions)
- A timestamp
- A unique cryptographic hash (a fixed-length string generated from the block’s data)
- The hash of the previous block

This linking via hashes creates the “chain.” Change anything in an earlier block, and its hash changes—breaking every link that follows. That makes tampering extremely difficult.

The process unfolds like this:

1. Someone initiates a transaction.
2. It’s broadcast to the network of nodes (computers).
3. Nodes validate it against the rules (e.g., confirming the sender has sufficient balance).
4. Valid transactions are collected into a candidate block.
5. Using a consensus mechanism—most famously Proof of Work (miners solve hard puzzles) or Proof of Stake (validators are chosen based on stake)—one node gets to add the block.
6. The new block is broadcast and appended to everyone’s copy of the chain.

Because thousands or millions of independent nodes maintain identical copies and constantly check each other, no single party can alter the record without overwhelming network agreement.

The outcome: a transparent, immutable, trustless system where participants rely on mathematics and cryptography instead of intermediaries. This foundation powers cryptocurrencies, supply-chain tracking, smart contracts, digital identity, and more.