TinyMerkleTree

A TypeScript implementation of an incremental Merkle tree with O(log N) inserts and O(depth) storage. Inspired by Solidity on-chain designs, this library is perfect for off-chain computation, ZK-friendly trees, or light client state tracking.

It is highly compatible and a remake of the merkle tree at Solidity Merkle Tree.

Features

• Incremental, append-only Merkle tree.
• O(log N) insertion per leaf.
• Fixed depth, supports billions of leaves.
• Only stores the last unresolved hash per depth.
• Deterministic, Poseidon-style hash compatible.
• Fully typed for TypeScript projects.

Installation

npm install @fifteenfigures/tiny-merkle-tree
# or
yarn add @fifteenfigures/tiny-merkle-tree

Usage

import { TinyMerkleTree } from "@fifteenfigures/tiny-merkle-tree";

const leaves = ["0x...", "0x...", "0x...", "0x..."]
const tree = new TinyMerkleTree([leaves]);
const root = tree.root

Concepts

Tree Structure

Depth 3 (root)          H7
                       /  \
Depth 2             H5      H6
                    / \    / \
Depth 1           H1  H2  H3  H4
                  |   |   |   |
Depth 0 (leaves)  L0  L1  L2  L3

• Leaves at depth 0
• Internal nodes store the last unresolved hash at each depth
• Depth indices start at 0 → DEPTH