About Line Shuffler

Randomly shuffle every line in your input — Fisher-Yates, deterministic. Part of the DevTools Surf developer suite. Browse more tools in the Text / String collection.

Use Cases

• Teachers randomizing student name lists for fair group assignments
• QA engineers shuffling test cases to detect order-dependent bugs
• Data scientists randomizing dataset rows before train/test splitting
• Game developers shuffling question banks or card decks for gameplay

Tips

• The Fisher-Yates algorithm ensures each permutation is equally likely
• Shuffle test data lines to randomize input order for unbiased testing
• Re-shuffle multiple times to verify results differ each run

Fun Facts

• The Fisher-Yates shuffle was originally described by Ronald Fisher and Frank Yates in 1938 using pencil and paper — the modern computer version was published by Richard Durstenfeld in 1964.
• A naive shuffle that swaps each element with a random position produces biased results — the Fisher-Yates algorithm is O(n) and provably uniform.
• There are n! possible permutations of n lines — for just 20 lines, that's 2,432,902,008,176,640,000 (about 2.4 quintillion) possible arrangements.

FAQ

Is the shuffle truly random?

Fisher-Yates with the browser's crypto.getRandomValues — cryptographically strong. For reproducibility, supply a seed and the same seed produces the same order.

Can I shuffle a subset of lines?

Toggle 'preserve header rows' to keep the first N lines fixed (CSV headers, config prefixes). Everything below shuffles.

Does it preserve blank lines?

Optional. Default includes them as shuffleable entries. Toggle 'skip blanks' to keep them as separators in their original positions.

What's a practical use case?

Randomizing test order, generating demo playlists, anonymizing exam questions, or creating a randomized quiz from a flat list.