Cron Expression Generator & Explainer Online Free
Five fields, cryptic wildcards, surprising traps — cron is powerful but easy to misread. This generator lets you pick minute, hour, day-of-month, month and day-of-week values from friendly controls (or paste an existing expression) and immediately shows both the cron string and a plain-English description of what it does. Validation flags out-of-range values and conflicting day-of-month/day-of-week rules, so you ship schedules that actually fire when you expect.
Cron Expression Generator & Explainer In-Browser Workspace
Input data or select files to begin. 100% private, client-side execution with zero server transmission.
How to Use Cron Expression Generator & Explainer
- Step 1: Select values for each field: minute, hour, day of month, month and day of week.
- Step 2: Or paste an existing cron expression to load and edit its fields.
- Step 3: Read the generated expression and its English description updating live.
- Step 4: Check the validation panel for range errors or OR-conflicts between day fields.
- Step 5: Copy the final cron string into crontab, CI config or your job scheduler.
About Cron Expression Generator & Explainer
A standard cron line is "m h dom mon dow" plus the command. Minute accepts 0–59, hour 0–23, day-of-month 1–31, month 1–12 (or names like JAN), day-of-week 0–7 (0 and 7 = Sunday). Each field supports * (every), a single value, lists (1,15), ranges (1-5), steps (*/15 or 10-40/5) and combinations. When both day-of-month and day-of-week are restricted (neither is *), cron runs the job when EITHER matches — an OR, not AND — which is the most common production surprise: "0 0 1 * 1" fires on the 1st AND on Mondays, not only Mondays that are the 1st. This tool explains that rule in the description. The generator builds expressions from your selections using * for untouched fields, comma lists for scattered picks and */n steps for regular intervals. Validation checks each numeric token against its field range, rejects malformed wildcards, and warns about the day-field OR semantics. The humanizer expands expressions into phrases like "At 02:30 on every day-of-month 1 and on every day-of-week Monday" or "Every 15 minutes between 09:00 and 17:00 on weekdays". Next-run estimation advances a timestamp field-by-field to show approximately when the schedule fires next (server timezone assumed). Remember cron uses the system timezone of the machine that runs it — UTC on most cloud boxes — so align your mental model accordingly before relying on the preview.
Frequently Asked Questions
What cron flavor does this generate?
Standard five-field cron used by Linux, macOS and most schedulers; some SaaS tools use six fields with seconds.
Why does my day-of-month job also run on weekdays?
When both day fields are restricted cron ORs them; use * for one field if you need AND-like behavior via wrappers.
Can I use month or day names like MON and JAN?
Yes — names are accepted on input and normalized to numbers in the generated string for portability.
Does the next-run preview use my timezone?
Preview assumes the server timezone; always confirm your scheduler’s TZ environment variable.
Are seconds and years fields supported?
Quartz-style year fields and 6-field seconds syntax are out of scope; stick to classic five-field expressions.