Cron Expression Generator -- Build & Test Cron

Cron Expression Generator

Build cron expressions visually, or paste an existing one to decode it. All computation runs locally in your browser.

Decode an Existing Cron Expression

Paste a cron expression below to decode it into a human-readable description and load it into the builder.

Cron Syntax Reference

A standard cron expression consists of five fields. The extended format adds a seconds field at the beginning.

 ┌───────────── minute (0-59)
 │ ┌───────────── hour (0-23)
 │ │ ┌───────────── day of month (1-31)
 │ │ │ ┌───────────── month (1-12)
 │ │ │ │ ┌───────────── day of week (0-6, Sun=0)
 │ │ │ │ │
 * * * * *

Field Ranges

Common Cron Expression Examples

How Cron Works

Cron is a time-based job scheduler found in Unix-like operating systems. It was first introduced in Version 7 Unix in 1979 and remains one of the most widely used scheduling utilities. The name comes from "chronos," the Greek word for time.

A cron daemon runs in the background and checks once per minute whether any scheduled jobs need to run. Jobs are defined in a file called the crontab (cron table), where each line contains a cron expression followed by the command to execute.

Standard vs. Extended Format

The standard cron format uses five fields (minute, hour, day of month, month, day of week). Many modern tools and frameworks -- including Quartz Scheduler (Java), Spring Framework, AWS EventBridge, and some CI/CD systems -- support a six-field format that adds a seconds field at the beginning. This generator supports both formats.

How Fields Combine

The minute, hour, and month fields use AND logic: all must match for the job to run. Day of month and day of week use OR logic in most implementations: the job runs if either field matches. For example, 0 0 15 * 5 runs at midnight on the 15th of every month AND every Friday -- not only on Fridays that fall on the 15th.

Timezone Considerations

Cron expressions do not include timezone information. The schedule executes in the timezone configured on the server or platform running the cron daemon. This tool calculates next-run times using your browser's local timezone. When deploying cron jobs to servers, always verify the server's timezone setting.

Frequently Asked Questions

What is a cron expression?

A cron expression is a compact string that defines a recurring schedule. Standard cron uses five space-separated fields: minute, hour, day of month, month, and day of week. Each field can contain numbers, wildcards (*), ranges (1-5), lists (1,3,5), or step values (*/10) to specify when a task should execute.

How do I read a cron expression?

Read it left to right through the five (or six) fields. For example, 30 9 * * 1-5 means: at minute 30 of hour 9 (9:30 AM), on every day of the month, in every month, on weekdays (Monday through Friday). The asterisk means "every possible value" for that field.

What does */5 mean?

The / character defines a step value. */5 in the minute field means "every 5th minute starting from 0," which produces: 0, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55. You can also specify a starting point: 3/5 means "every 5 minutes starting at minute 3" (3, 8, 13, 18, ...).

When should I use 6-field cron?

Use the 6-field format when your platform supports it and you need sub-minute precision. Java applications using Quartz Scheduler or Spring's @Scheduled annotation commonly use 6-field cron. Standard Linux/macOS crontab uses only 5 fields and does not support seconds.

Can I use names for months and days?

Some cron implementations accept three-letter abbreviations (JAN, FEB, MON, TUE, etc.), but this varies by platform. For maximum compatibility, use numbers: 1-12 for months and 0-6 for days of the week (where 0 = Sunday). This tool uses numeric values.

How do day-of-month and day-of-week interact?

In most standard cron implementations, when both day-of-month and day-of-week are specified (not *), the job runs when EITHER condition is met (OR logic). For example, 0 0 1 * 5 runs at midnight on the 1st of every month AND every Friday. Some non-standard implementations (like Quartz) use AND logic instead.

Does this tool store my data?

No. Everything runs in your browser. No data leaves your device.

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Privacy

This cron expression generator runs entirely in your browser. No expressions, schedules, or any other data are transmitted to any server. Nothing is stored or tracked.

Cron Expression Generator FAQ