What is a cron expression?
A cron expression is a string of five or six fields representing a schedule — minute, hour, day of month, month, day of week, and optionally year. Cron is used to schedule recurring tasks in Unix systems, CI/CD pipelines, and cloud services. This tool translates cron syntax into plain English and calculates upcoming execution times.
What a cron expression is
A cron expression is a compact schedule used by Unix cron and many job schedulers to say when a task should run. It is a set of fields — minute, hour, day of month, month, and day of week — each holding a number, a range, a list, or a wildcard. Reading one at a glance is hard, so this parser translates an expression into plain English and shows the next times it will fire.
Getting a schedule wrong is a common and costly mistake — a job that runs every minute instead of every day, or never at all — so confirming what an expression means before deploying it is well worth the moment it takes.
The five fields
From left to right the fields are minute (0–59), hour (0–23), day of month (1–31), month (1–12), and day of week (0–6, where 0 is Sunday). A star means every value, a comma lists several, a hyphen gives a range, and a slash sets a step — so */15 in the minute field means every fifteen minutes.
Testing before you deploy
The safest way to trust a schedule is to read its plain-English description and check the next few fire times before deploying. A single wrong field can turn 'daily at midnight' into 'every minute', so confirming the upcoming runs match your intent prevents a job from silently overloading a system.
How to read a cron expression
- 1Enter the expression. Paste a five-field cron expression such as 0 9 * * 1.
- 2Click Parse. See a plain-English description of the schedule.
- 3Check the next runs. Review the upcoming fire times to confirm the schedule is what you intended.
Examples
Every weekday at 9am
Input
0 9 * * 1-5
Output
At 09:00, Monday through Friday
Every 15 minutes
Input
*/15 * * * *
Output
Every 15 minutes
First of the month
Input
0 0 1 * *
Output
At 00:00 on day 1 of every month
Cron fields and symbols
The five fields and what the symbols mean.
| Field / symbol | Meaning |
|---|---|
| Minute | 0–59 |
| Hour | 0–23 |
| Day of month | 1–31 |
| Month | 1–12 |
| Day of week | 0–6 (Sun=0) |
| * | Every value |
| */n | Every n (step) |
| a-b | Range |
| a,b | List |
Frequently asked questions
What do the five fields mean?+
In order: minute, hour, day of month, month, and day of week. Each accepts a number, a range, a list, a step, or a star for every value.
What does an asterisk mean?+
A star matches every value for that field. Five stars, * * * * *, means run every minute.
How do I run a job every N minutes?+
Use a step in the minute field: */15 * * * * runs every fifteen minutes, and */5 every five.
How do day of month and day of week interact?+
When both are set, most cron implementations run the job when either field matches, which can cause more runs than expected — check the parsed description to be sure.
Is my expression sent anywhere?+
No. Parsing happens in your browser.
Is it free?+
Yes — free with no limits.
Do cron times use UTC or local time?+
It depends on the server or scheduler running the job. Many run in UTC, so always confirm the timezone of the system that will execute the expression.