Block
A block is a batch of validated Bitcoin transactions bundled together with a header containing metadata, a timestamp, and a reference to the previous block. Blocks are added to the blockchain approximately every 10 minutes through the mining process.
How It Works
A Bitcoin block consists of two main parts: the block header and the transaction data. The header contains the previous block's hash, a Merkle root summarizing all transactions in the block, a timestamp, the difficulty target, and a nonce that miners iterate to find a valid proof-of-work. The transaction data includes all the individual transactions the miner selected from the mempool.
Blocks have a maximum weight of 4 million weight units (roughly equivalent to about 1-1.5 MB of raw data depending on transaction types). Miners select which transactions to include, typically prioritizing those with higher fee rates measured in sats per vbyte. The first transaction in every block is the coinbase transaction, which creates new bitcoins as the miner's reward.
The difficulty adjustment algorithm ensures blocks are found approximately every 10 minutes on average, regardless of how much mining power joins or leaves the network. This predictable block time is fundamental to Bitcoin's monetary policy and transaction settlement guarantees.
Key Points
- Blocks are found approximately every 10 minutes on average
- Each block references the previous block's hash, creating the chain
- Maximum block weight is 4 million weight units (introduced by SegWit)
- The coinbase transaction in each block creates new bitcoins
- More confirmations (blocks built on top) means greater transaction finality