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list-shuffler

A list shuffler reorders items into a random sequence — every permutation equally likely if the algorithm is fair. The naive "sort by random number" trick is biased; the correct algorithm is Fisher-Yates (also called Knuth shuffle), which iterates from the end and swaps each element with a random earlier or current element. The ZTools List Shuffler tool implements Fisher-Yates with a configurable RNG: Math.random (fast, fine for games and casual use) or crypto.getRandomValues (cryptographically secure, for raffles and prize draws where fairness can be challenged).

Use cases​

Run a fair raffle​

Paste participant names, shuffle, take the top N. Use the crypto-RNG mode so the draw is auditable as fair.

Randomise a quiz​

Question order shouldn't reveal patterns. Shuffle the answer list per session.

Distribute work randomly​

Pair-programming rotations: shuffle, then partition. Removes bias from "who works with whom".

Shuffle a playlist​

Spotify's shuffle is famously not uniform. A clean Fisher-Yates pass over your track list does what users expect.

How it works​

  1. Paste the list — One item per line. Empty lines preserved or skipped per toggle.
  2. Pick RNG — Standard (Math.random — pseudo-random, deterministic if seeded) or Cryptographic (crypto.getRandomValues — true randomness from the OS).
  3. Optionally seed — For reproducible shuffles (debugging, replays), provide a seed. Same seed + same input = same output.
  4. Shuffle and copy — Output is the shuffled list. Re-shuffle for a new order. Original list available alongside.

Examples​

Input: [A, B, C, D, E]

Output: One shuffle: [C, A, E, B, D]. Another shuffle: [B, D, A, C, E]. All 120 permutations equally likely.

Input: Seeded shuffle ("seed=42")

Output: Deterministic — every run with seed 42 produces the same result. Useful for tests and reproducible demos.

Input: Cryptographic shuffle of a 1,000-item raffle

Output: crypto.getRandomValues backs the RNG; an attacker can't predict the result without compromising the OS RNG.

Frequently asked questions​

Why not sort by a random number?

It's biased. JavaScript's sort calls the comparator multiple times per pair — the resulting permutation is not uniform. Fisher-Yates is the correct algorithm.

Is Math.random good enough?

For games, raffles among friends, randomising tests — yes. For high-stakes (real money raffles, security), use crypto.getRandomValues.

Can someone reverse-engineer the result?

With Math.random and known timing, a determined attacker could narrow down the seed. With crypto.getRandomValues, no — values are sourced from /dev/urandom equivalent.

Does the tool log my list?

No — pure browser. Lists never leave the device.

What's the largest list it handles?

Fisher-Yates is O(n). A million items shuffles in ~100 ms. Browser memory is the only ceiling.

How is this different from the List Randomizer?

Same operation under the hood. We keep both for SEO — different users search for different terms. Internally one shuffle implementation backs both.

Tips​

  • For raffles, paste participant names, run cryptographic shuffle, screenshot the result. Reproducible audit trail without exposing names elsewhere.
  • Seeded shuffles are great for unit tests — the test always sees the same "random" order.
  • If you need to draw N winners (without replacement), shuffle and take the first N. Drawing-with-replacement is a different operation — use the Random Picker tool.

Try it now​

The full list-shuffler runs in your browser at https://ztools.zaions.com/list-shuffler — no signup, no upload, no data leaves your device.

Open the tool ↗

Last updated: 2026-05-06 · Author: Ahsan Mahmood · Edit this page on GitHub