"If a Merkle tree commits to a million transactions and one of them is altered, the root changes. To prove inclusion of any one transaction, you only need ~20 hashes." Most explanations stop there and leave you to imagine the picture. This article is the picture: an interactive visualizer where you edit a leaf and watch the change ripple to the root, and a proof — the actual sibling hashes you'd send to a verifier — gets generated and replayed live.

🌳 Demo : https://sen.ltd/portfolio/merkle-viz/

📦 GitHub : https://github.com/sen-ltd/merkle-viz

The whole thing is ~200 lines of pure logic + 150 lines of DOM/SVG glue, no build step, no dependencies. Hashing is crypto.subtle.digest("SHA-256", …) in both the browser and Node 18+, so the same merkle.js ships to production and runs under node --test . 17 tests cover the math.

What a Merkle tree actually is

You have a list of items: transactions, log entries, file blobs, anything addressable.…