Blocks and Chains
How blocks link.
What Is a Block?
A block is the fundamental container in a blockchain. It bundles together a set of validated transactions along with metadata that ties it to the rest of the chain.
Each block has two main parts:
- Header — metadata (timestamp, hashes, nonce)
- Body — the list of transactions
Anatomy of a Block Header
The header is small but powerful. A typical Ethereum-style header includes:
previousHash— hash of the prior blocktimestamp— when the block was createdmerkleRoot— fingerprint of all transactionsnonce— value used in consensus
The header is what gets hashed to identify the block.
block Header {
previousHash: 0x9f1c...a3
timestamp: 1717000000
merkleRoot: 0x4be2...07
nonce: 42891
}All lessons in this course
- Blocks and Chains
- Merkle Trees
- Hashing in Blockchain
- Distributed Ledgers