CronLens

What is CronLens?

A "cron expression" is the string of numbers and symbols (like 0 9 * * 1-5) that Linux, CI pipelines and Kubernetes use to schedule a recurring job — but it's not written for humans to read at a glance. CronLens takes a cron expression and translates it into a plain-English sentence and a list of the next 10 times it will actually run, so you can double-check a schedule before you deploy it.

How to use CronLens

1. Type or paste your cron expression into the Cron expression field, or click one of the presets (like "Every 15 min" or "Weekdays 9 AM") to try an example.
2. Read the plain-English sentence above the run list to confirm the schedule means what you think.
3. Check the Next 10 runs panel to see the actual upcoming dates and times, in your local timezone.
4. Use the field breakdown (Min, Hour, DoM, Month, DoW) to see exactly what each part of the expression is doing.

How cron expressions work

A cron expression has 5 fields — minute hour day-of-month month day-of-week — each field a number, a range, a comma list, a step, or * (any value), per the Vixie Cron / POSIX standard:

0 9 * * 1-5
→ minute 0, hour 9, any day of month, any month, Monday(1) through Friday(5)
→ "At 9:00 AM, Monday through Friday"

One rule trips up a lot of people: if both day-of-month and day-of-week are restricted (not *), cron runs the job when either field matches — not only when both match at once. So 0 0 1 * 5 means "midnight on the 1st of the month, OR every Friday at midnight," not "only Fridays that happen to be the 1st." CronLens implements this exact OR rule.

Frequently asked questions

What format does CronLens expect?

Standard 5-field Vixie cron: minute, hour, day of month, month, day of week. It supports *, lists (1,15), ranges (1-5) and steps (*/15).

What happens if both day of month and day of week are set?

Per the cron standard, when both fields are restricted (not *), the job runs when EITHER one matches, not only when both match at once. CronLens follows this rule exactly.

What timezone are the next-run times shown in?

Your browser's local timezone, which is labeled above the list. Cron itself has no concept of timezone — it always runs in the timezone of the machine executing it.

Does it support 6-field cron with seconds, or @daily-style shortcuts?

Not currently. CronLens targets standard 5-field cron, the format used by crontab, most CI schedulers and Kubernetes CronJobs.