Merkle Root

The Merkle root is the single hash sitting at the top of a Merkle tree, summarising every transaction in a block in one fixed-length value. Miners or validators compute it by repeatedly hashing pairs of transaction hashes until only one value remains, then place it in the block header next to the timestamp, the difficulty target and the previous block's hash. Because the header is what consensus actually secures, the Merkle root binds a block's entire contents to its identity: alter, remove or reorder a single transaction and the root — and therefore the block hash — no longer matches. That same root is what compact inclusion proofs are checked against.