Cron Expression Parser
Parse cron expressions into human-readable descriptions and see the next scheduled execution times.
How It Works
The Cron Expression Parser takes a cron schedule expression — five fields (minute, hour, day-of-month, month, day-of-week) or six (with seconds prefixed) — and tells you in plain English what it means and when it will next run. Type an expression like 0 9 * * 1-5 or */15 9-17 * * * and the tool parses each field, validates the values against allowed ranges, and produces a human-readable description (‘At 09:00 on every weekday’) along with the next several scheduled run times computed from the current UTC clock. Standard cron syntax is supported: lists (1,3,5), ranges (1-5), step values (*/5, 0-30/10), and named tokens for months (JAN-DEC) and days of week (SUN-SAT). The tool warns about ambiguous DOM/DOW combinations (one of them must be * for sane behaviour) and rejects out-of-range values (60 for minute, 13 for month) inline. Parsing runs entirely in your browser, so confidential job schedules from production cron tables stay private.
Use Cases
- Verifying a scheduled job expression before deploying it
- Understanding an inherited cron job at a glance
- Checking how often a task will run over the next week
- Debugging why a cron job fired at an unexpected time
Frequently Asked Questions
- Does this support 5-field or 6-field cron syntax?
- Both. Five fields (minute hour DOM month DOW) is classical UNIX cron; six fields prefix seconds and is used by Quartz, Spring, and other modern schedulers.
- What about the special characters L, W, and #?
- Some Quartz-style extensions (L, W, #) are not part of standard UNIX cron and may not be supported. Stick to standard wildcards, lists, ranges, and step values for portability.
- Why is DOM/DOW special?
- UNIX cron treats specifying both day-of-month AND day-of-week as an OR (rare, often unintended). For predictable behaviour, set one of them to *.
- What time zone are the next-run times in?
- UTC by default. Many cron daemons run in the system's local time zone — adjust accordingly when comparing to a production schedule.
- Is my expression sent anywhere?
- No. Parsing and next-run calculation happen entirely in your browser.