🌳 Merkle Tree Hash Proofs

About this simulation

A Merkle tree hashes data blocks in pairs, repeatedly, until a single root hash remains. That one root — a few bytes — commits to every record beneath it: change a single byte anywhere in the dataset and the root changes too. This is how blockchains, Git, package managers and certificate transparency logs let you verify one record is included in a huge dataset without downloading the whole thing.

How it works

• Each leaf is hash(record). Each internal node is hash(left child + right child), all the way up to the root.
• To prove a leaf is part of the tree, you only need the leaf itself and the sibling hash at every level on the way to the root — that's log₂(n) hashes for n leaves, not n.
• A verifier recomputes the hashes along that path and checks the result matches the trusted root it already has (e.g. from a block header).
• Tampering with a leaf changes every hash above it, so the recomputed root no longer matches the trusted root — the forgery is detected instantly.

Controls

• Leaf count — how many data blocks the tree holds (4–32).
• Leaf to verify — pick which record's inclusion proof to highlight.
• 🧪 Tamper selected leaf — corrupt that record's data and watch the recomputed root diverge from the trusted root.
• ▶ Auto-verify pulse — animate a hash computation traveling from the leaf up to the root.
• ↺ New random tree — regenerate the dataset with fresh random records.

Did you know?

Ralph Merkle patented this structure in 1979. Bitcoin uses a Merkle tree of transactions so light clients can verify a transaction is in a block using only ~log₂(n) hashes instead of downloading every transaction — for a block with 2,048 transactions, that's just 11 hashes.