What is a cron expression?

A cron expression is a string of five or six fields that represent a schedule. Cron is a time-based job scheduler in Unix-like operating systems. The expression defines when a command or script should run. Each field represents: minute, hour, day of month, month, and day of week. Some systems support a sixth field for seconds.

The step value (/) means every Nth. So */5 in the minute field means every 5 minutes (0, 5, 10, 15, ...). You can combine it with ranges: 1-30/5 means every 5 minutes from minute 1 to 30 (1, 6, 11, 16, 21, 26).

What does the asterisk (*) mean?

The asterisk (*) is a wildcard that means every possible value for that field. For example, * in the minute field means every minute, and * in the hour field means every hour. So * * * * * runs every minute of every hour of every day.

How do I run a job on weekdays only?

Use 1-5 in the day of week field to specify Monday through Friday. For example, 0 9 * * 1-5 runs at 9:00 AM every weekday. Days are numbered 0-6 where 0 is Sunday and 6 is Saturday. You can also use names: 0 9 * * MON-FRI.

What is the difference between 5 and 6 field expressions?

Standard Unix cron uses 5 fields: minute, hour, day of month, month, day of week. Some systems (like Quartz scheduler, Spring, and some cloud platforms) support a 6th field for seconds at the beginning. The 6-field format allows scheduling at second-level precision, useful for applications requiring more granular timing.

What timezone does cron use - server time or UTC?

Cron jobs run based on the server's local timezone. If your server is set to UTC, cron runs in UTC. If it's in PST, cron runs in PST. Cloud platforms like AWS and GCP default to UTC for consistency across distributed systems.

How do day of month and day of week interact?

In standard cron behavior, if both day of month and day of week are specified (not *), they create an OR condition - the job runs if EITHER condition is met. For example, 0 0 1,15 * 5 runs at midnight on the 1st and 15th of every month, AND every Friday. If you want AND logic, you may need to use script logic.

Do cron jobs automatically adjust for daylight saving time (DST) transitions?

Yes, cron follows the server's timezone settings, including DST transitions. During spring forward (when clocks jump ahead an hour), jobs scheduled during the skipped hour won't run that day. During fall back (when an hour repeats), jobs may run twice.

Is my data stored or transmitted?

No. All processing happens entirely in your browser using JavaScript. No data is ever transmitted to any server. This means your cron expressions and schedules remain completely private. The tool works fully offline once the page is loaded.

How can I schedule a cron job to run just once at a specific time instead of repeatedly?

Cron is designed for recurring tasks, not one-time execution. For one-time scheduled tasks, use at command on Unix systems or Task Scheduler on Windows. If you must use cron, create an expression like 30 14 25 12 * for December 25 at 2:30 PM, then manually remove the crontab entry after execution.

Cron Expression Generator
Visual Cron Builder

Build cron schedules visually. Generate human-readable descriptions and preview next execution times. 100% client-side. Zero data stored.

Visual Builder

Include seconds

Minute

0-59

Hour

0-23

Day (Month)

1-31

Month

1-12 or JAN-DEC

Day (Week)

0-6 or SUN-SAT

Cron Syntax

* Any value

1,3,5 List

1-5 Range

*/5 Every 5th

Generated Expression

0 0 * * *

Valid

Description

At 12:00 AM

Copies: */5 * * * * /path/to/command
Ready to paste into your crontab file - just replace the path

Next Executions

Timezone:

Parse Expression

Enter a cron expression to parse and validate it.

Common Presets

Quick Reference

Field Order (5 fields)


                                        minute hour day month weekday

Field Order (6 fields)


                                        second minute hour day month weekday

Special Characters

* - Every value
, - Multiple values
- - Range of values
/ - Step values

Day of Week

0 = Sunday, 1 = Monday, ..., 6 = Saturday
Also accepts: SUN, MON, TUE, WED, THU, FRI, SAT

Month Names

1 = January, 2 = February, ..., 12 = December
Also accepts: JAN, FEB, MAR, APR, MAY, JUN, JUL, AUG, SEP, OCT, NOV, DEC

Privacy First

All parsing and generation happens locally in your browser. No data is sent to any server.

Common Use Cases

Database Backups

Schedule daily backups at 2 AM when server load is lowest. Use "0 2 * * *" for reliable nightly database snapshots.

Report Generation

Generate weekly analytics reports every Monday morning. Use "0 9 * * 1" to deliver fresh insights at the start of each week.

Cache Cleanup

Clear temporary files every hour to prevent storage bloat. Use "0 * * * *" for automatic hourly cleanup.

Email Reminders

Send reminder emails every weekday at 8 AM. Use "0 8 * * 1-5" to automate daily notifications during business days.

Data Synchronization

Sync data between systems every 15 minutes. Use "*/15 * * * *" for frequent, reliable data replication.

Health Checks

Monitor server health every 5 minutes. Use "*/5 * * * *" to catch issues quickly and maintain uptime.

Frequently Asked Questions

Why We Built This Cron Generator

Cron expressions are powerful but cryptic. A simple typo can mean the difference between running a backup daily at 2 AM versus every minute of every day. We built this visual cron generator to eliminate guesswork and prevent costly scheduling mistakes. Whether you're a DevOps engineer setting up automated deployments or a developer configuring background jobs, building schedules visually is faster and safer than memorizing syntax.

Unlike online tools that send your cron expressions to external servers, our generator processes everything locally using JavaScript. This means your automation schedules never leave your computer. The tool works completely offline once loaded, making it safe for enterprise environments and air-gapped systems. Preview execution times in your timezone, generate human-readable descriptions, and validate expressions instantly - all without network access.

The Cron Expression Generator is part of RJL.io's collection of free developer tools - each designed to do one thing exceptionally well, with no accounts, no tracking, and no data collection. Check out our other tools: UUID Generator, QR Code Generator, Base64 Encoder, and more. Every tool is 100% client-side, works offline, and respects your privacy.

Cron Expression Generator Visual Cron Builder