Block

A block is a batch of transactions bundled together and added to a blockchain as one unit. Blocks are the “pages” of the ledger, added in sequence and linked to form the chain.

How it works

Each block contains a set of validated transactions, a timestamp, and a cryptographic reference to the previous block, which is what chains them in order. The network’s consensus mechanism decides who gets to add the next block; on a proof-of-work chain that is the winning miner, who also receives the block reward. Once added and confirmed by later blocks, a block’s contents become very hard to change.

Why it matters

Grouping transactions into linked blocks is what gives a blockchain its tamper-resistant order. A block’s size and how often blocks are produced also shape a network’s capacity and fees.

Example

The very first block of a blockchain is called the genesis block, the foundation every later block builds on.