Merkle Root

The single hash at the top of a Merkle Tree that summarizes all transactions or data in a blockchain block.

What is Merkle Root?

The Merkle Root is the topmost hash in a Merkle Tree, representing a cryptographic summary of all transactions or data entries within a blockchain block. It is generated by recursively hashing pairs of child nodes in the Merkle Tree until a single hash remains. In Ethereum, the Merkle Root is included in a block’s header to provide a compact way to verify the integrity and inclusion of all transactions (via the transaction trie), receipts (via the receipt trie), or state data (via the state trie) in that block.

In Ethereum’s mainnet, each block contains three Merkle Roots: one for the state trie (account data), one for the transaction trie (all transactions in the block), and one for the receipt trie (transaction outcomes). For example, the transaction trie’s Merkle Root allows nodes to confirm that a specific transaction is part of a block using a Merkle proof, which requires only a small subset of hashes rather than the entire block’s data. This efficiency is crucial for light clients and enhances Ethereum’s scalability by enabling quick verification of digital asset transactions and state changes.