Random Cron Expression Generator

What it does

The Random Cron Expression Generator produces Unix cron schedules in the standard 5-field format (minute, hour, day-of-month, month, day-of-week). Choose common style for the patterns humans actually write — daily at noon, every 15 minutes, weekday mornings — or random for arbitrary valid expressions that stress-test parsers. Up to 1,000 per run, seeded.

Common use cases

• Cron parser testing — valid expressions across the full field syntax (ranges, steps, lists, wildcards) for parsing and next-run calculation code.
• Scheduler fixtures — populate job tables in scheduling systems and admin UIs with plausible schedules.
• Config generation — realistic schedule values for generated configs and documentation examples.
• UI testing — cron-describer components (“runs every day at 12:00”) fed varied input.

Settings

• Style — common (human-typical patterns) or random (arbitrary valid expressions); a preset for each.
• How many — 1 to 1,000 expressions, exportable as text, CSV, or JSON.
• Seed — the same seed and style regenerate the identical list.

Privacy note

Expressions are generated locally in your browser and never uploaded. They’re synthetic schedules — they don’t run anything until you put them somewhere that does.

FAQ

Quick refresher on the five fields? minute hour day-of-month month day-of-week — so 0 12 * * 1-5 is weekdays at noon, */15 * * * * is every 15 minutes.

Why test with random expressions? Because users write cron you’d never write. Step values on ranges, long lists, and odd field combinations are all valid — a parser that only met 0 0 * * * in testing will meet the rest in production.

Do these cover seconds or year fields? The output is classic 5-field cron. Extended formats (Quartz’s seconds field) differ by system — check what your scheduler expects.