What is a Merkle tree?

A Merkle tree fingerprints a long list with one short value, the root, so that anyone can prove an item is in the list with a handful of hashes instead of the whole list.

Also called hash tree.

How it works

Every item is hashed, pairs of hashes are hashed together, and so on up to a single root. To prove that an item is included, you show the hashes along its path to the root.

Where it is used

Bitcoin blocks commit to their transactions with a Merkle root. Shielded pools keep their note commitments in a Merkle tree, and a zero-knowledge proof shows that a note is in the tree without revealing where.

In Redacted

Redacted’s note tree is append-only and 4.3 billion slots deep. Proving that a note is in it always takes thirty-two hashes, whether it is the fourth note or the four billionth.

Architecture →

Related terms

CommitmentA commitment locks in a piece of data without revealing it. Later it can be opened and anyone can check that it matches, but until then it gives nothing away and cannot be changed.Zero-knowledge proofA zero-knowledge proof lets someone prove that a statement is true without revealing anything else, for example that they own funds and may spend them, without showing which funds or who they are.Shielded poolA shielded pool holds funds as private notes inside a smart contract. Deposits and withdrawals are public, but what happens inside is proved with zero-knowledge proofs and does not reveal who owns what.

Sources: Merkle tree, Wikipedia · Bitcoin whitepaper

Updated October 7, 2026. All terms