Amidakuji (Ghost Leg) maker: a fair random pairing tool for up to 200 people, entirely in the browser

Amidakuji is the Japanese ladder lottery: names go along the top, prizes or roles along the bottom, and each person traces a path down a ladder with random rungs. Every name lands on exactly one result, and nobody can predict it. Offices in Japan use it for seating, task assignment and drawing lots. I built a browser version that works for up to 200 people.

Amidakuji maker

How it works

  • Enter names (and optionally results). Paste a column from a spreadsheet and the rows fill in automatically; tab-separated "name → result" pairs work too.
  • Press Draw and watch each path animate down the ladder, or reveal them one at a time.
  • Nothing is sent to a server. The whole lottery (names, results, and the random seed for the rungs) lives in the URL after the #, so you can hand the link to others and they will open exactly the same ladder.
  • Cheat prevention: turn it on and the results stay hidden until every path has been traced. Redrawing changes the seed, so a new link means a new draw.
  • Share: one button creates a short URL and a QR code, handy when the ladder is on a meeting-room screen and everyone opens it on their phone. A short URL is only created when you ask for it, and it is deleted after a year without access.
  • Group mode splits people into teams instead of assigning results.

Why the ladder is a single number

The rungs are generated from a 32-bit seed with a deterministic random generator (mulberry32). The same seed always produces the same ladder, in any browser. That is what makes the link shareable without storing anything, and it keeps the URL short: it carries the names, not the ladder.

👉 Amidakuji (Ghost Leg) maker — also available in Japanese, Chinese, Korean, Spanish, French, German, Portuguese, Russian, Hindi and Arabic.

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