List Shuffler — Randomize Line Order Online

What is List Shuffler?

List shuffling is the elementary operation of putting things in random order. Its correctness is deceptively subtle — the widely-copied `arr.sort(() => Math.random() - 0.5)` produces a biased permutation because JavaScript's sort algorithm assumes a consistent comparator. The correct algorithm is Fisher-Yates (also called Knuth shuffle): iterate from the end, and swap each element with a random one from itself to the current position. This tool implements Fisher-Yates directly, so every possible ordering of your list is equally likely.

How to shuffle a list online

1. 1Paste your list, one item per line.
2. 2Toggle 'trim whitespace' and 'ignore empty lines' if needed.
3. 3Click Shuffle — the output is a uniform random permutation.
4. 4Click again for a fresh shuffle — each click uses a new random seed.

Use Cases

Tips & Best Practices

• ▸Never use `arr.sort(() => Math.random() - 0.5)`. It's biased in every major JS engine — some elements are more likely to stay near their starting position.
• ▸Fisher-Yates is O(n) — it can shuffle millions of items in a fraction of a second.
• ▸For repeatable shuffles (unit tests), do it in code with a seeded PRNG. This tool always uses fresh Math.random.