Cron Expression Builder

Cron syntax is compact by design — five fields packed into one line like 0 9 * * 1-5 — which makes it fast to write once you know it and completely opaque if you don't. This cron expression builder lets you set each field individually with plain text inputs, shows a live human-readable description of what you've built, and lists sample upcoming run times so you can sanity-check the schedule before you deploy it anywhere.

Nine common presets cover the schedules most people actually need — every 5 minutes, every weekday at 8 AM, the first of the month, and similar patterns — so you can start from something close and adjust individual fields rather than building an expression from a blank line. The description panel updates instantly as you type, translating symbols like */5 or 1-5 into a plain-English sentence.

Everything runs client-side in your browser using plain JavaScript, with no server involved and no cron daemon actually running anywhere — this is a syntax builder and explainer, not a live scheduler. Once you've got the expression you want, copy it into whatever actually executes your job: a crontab file, a CI pipeline's schedule trigger, or a cloud scheduler.

A cron expression is five space-separated fields, always in the same order: minute (0–59), hour (0–23, 24-hour clock), day of month (1–31), month (1–12), and day of week (0–6, where 0 is Sunday). The expression 30 14 * * * means minute 30, hour 14, every day of the month, every month, every day of the week — in other words, 2:30 PM daily.

Each field accepts an asterisk to mean "any value," a specific number, or the special characters covered below for steps, ranges, and lists. There's no sixth field for seconds in standard cron — if you need sub-minute precision, cron itself isn't the right tool and you'll need a different scheduler that supports it.

Every 5 minutes is */5 * * * * — the step value in the minute field alone is enough, since every other field stays wide open with an asterisk. Every weekday at 8 AM is 0 8 * * 1-5 — minute 0, hour 8, any day of month, any month, weekdays 1 through 5 (Monday through Friday, since 0 is Sunday and 6 is Saturday).

The first day of every month at midnight is 0 0 1 * * — the day-of-month field is locked to 1 while everything else stays open. A single weekly run, like every Monday at 9 AM, is 0 9 * * 1. All four of these are available as one-click presets in the builder above, and each one also fills in the individual minute/hour/day/month/weekday fields so you can see exactly which piece controls which part of the schedule.

• */5 * * * * — every 5 minutes
• 0 8 * * 1-5 — every weekday at 8:00 AM
• 0 0 1 * * — midnight on the 1st of every month
• 0 9 * * 1 — every Monday at 9:00 AM
• 0 0 * * 0 — midnight every Sunday

The asterisk (*) means "every value is fine" for that field. A hyphen defines an inclusive range, like 1-5 for Monday through Friday in the weekday field, or 9-17 for the hours 9 AM through 5 PM. A slash after an asterisk or a range defines a step value — */15 in the minute field means every 15 minutes, and 0-30/10 would mean every 10 minutes between :00 and :30.

A comma lists out specific, non-consecutive values in one field, such as 1,15 in the day-of-month field to run on both the 1st and the 15th. Standard cron parsers support all four of these, but this builder's plain-English description only translates asterisks, step values, and hyphen ranges into a sentence — a comma-separated list is shown as the raw field value rather than spelled out, so double-check a list-based field by reading the numbers directly rather than relying on the description text for that field.

The "Next 5 Executions" panel steps forward minute by minute from right now and lists the next five timestamps that match your minute and hour fields, which is a fast way to confirm that a time-of-day schedule like "every day at 2:30 PM" is actually landing on the time you intended.

That preview only checks the minute and hour fields, though — it does not filter by day of month, month, or day of week. If you've built a schedule restricted to weekdays only, or the first of the month only, the listed "next runs" will still show every day at that time, not just the days your expression actually restricts it to. Treat the preview as a check on the time-of-day portion of your schedule, and verify day/month/weekday restrictions by reading the expression itself or testing it in your actual scheduler.

In most cron implementations, when both the day-of-month and day-of-week fields are restricted to something other than an asterisk, the two conditions are combined with OR, not AND — the job runs if either condition matches, not only when both do. An expression like 0 0 15 * 1 doesn't mean "the 15th, but only if it's a Monday"; it means "midnight on the 15th, and also midnight every Monday."

The clean way to avoid this surprise is to leave one of the two fields as an asterisk whenever you're scheduling by the other — use day-of-month alone for "the 15th of every month" and day-of-week alone for "every Monday," rather than trying to combine both into one field pair.

A standard crontab entry (edited with crontab -e on Linux or macOS) pairs the five-field expression with the actual command to run, and typically executes in the system's local timezone unless configured otherwise. GitHub Actions accepts the same five-field syntax under a workflow's schedule: cron: key, but always runs in UTC and only guarantees roughly five-minute scheduling precision, not exact-second timing.

Cloud schedulers like AWS EventBridge Scheduler and Google Cloud Scheduler also accept standard cron syntax (sometimes alongside their own alternative rate-expression format), generally defaulting to UTC as well unless you explicitly set a timezone. Whichever platform you're deploying to, it's worth confirming its timezone default before trusting a schedule you built assuming local time.