Cron Expression Generator

Easily generate cron expressions for scheduled tasks

Cron Expression Generator is a free online tool for intuitively creating cron expressions for scheduled tasks in Linux/Unix, Docker, Kubernetes, GitHub Actions, and more. Simply select minute, hour, day, month, and weekday to instantly generate accurate cron expressions with next execution time preview. Perfect for crontab, CI/CD pipelines, and batch processing configuration.

How to Use

Using the Cron Expression Generator is very simple:

Step 1: Select Schedule
Select when you want your task to run in each field: minute, hour, day, month, and weekday. You can also use presets (every hour, every day, every week, every month).
Step 2: Review Cron Expression
Based on your selection, a standard cron expression (5-field format) is automatically generated. The next scheduled execution times are also displayed in real-time.
Step 3: Copy and Use
Copy the generated cron expression and paste it into your configuration files such as crontab, Docker Compose, Kubernetes CronJob, or GitHub Actions.

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Practical Use Cases for Cron Expression Generator

Cron expressions are used in various automation scenarios including system administration, DevOps, and CI/CD pipelines:

1. Linux/Unix crontab (Scheduled Tasks)

When running scripts periodically on Linux servers, register cron expressions in crontab. Examples: Run backup script at 2 AM daily (0 2 * * *), run log rotation every Sunday (0 0 * * 0), etc.

2. CI/CD Pipelines (GitHub Actions, GitLab CI)

GitHub Actions schedule triggers and GitLab CI scheduled pipelines use cron expressions to automate periodic builds, tests, and deployments. Example: Run test suite daily at 3 AM (0 3 * * *).

3. Kubernetes CronJob

Kubernetes CronJob resources use cron expressions to periodically execute containerized tasks. Example: Run database backup job daily at 1 AM (0 1 * * *).

4. Docker Compose Scheduler

When using ofelia (Docker job scheduler) with Docker Compose, you can use cron expressions to periodically execute container tasks.

5. Monitoring & Alerts (Prometheus, Grafana)

Cron expressions are used for periodic tasks in monitoring tools such as Prometheus rule evaluation and Grafana alert sending.

6. Backup Automation

Use cron expressions for schedules to periodically execute backups of databases, file systems, and cloud storage.

7. Log & Temporary File Cleanup

Used for scheduling cleanup scripts that periodically delete old log files and temporary files.

What is a Cron Expression? Understanding the Mechanism

A cron expression is a format used to define task execution schedules in the Unix/Linux job scheduler 'cron'. It is now widely adopted across cloud services, CI/CD tools, and container orchestration platforms.

Basic Cron Expression Format (5 Fields)

A standard cron expression consists of 5 fields:

Minute (0-59): Minute to execute the task
Hour (0-23): Hour to execute the task (24-hour format)
Day (1-31): Day to execute the task
Month (1-12): Month to execute the task
Weekday (0-7): Day of week to execute the task (0 and 7 are Sunday)

Cron Expression Syntax

Each field can use the following notation:

* (asterisk): All values (means 'every')
Number: Specific value (e.g., 5 = minute 5, 14 = hour 14)
Comma (,): Multiple values (e.g., 1,15,30 = minutes 1, 15, 30)
Hyphen (-): Range (e.g., 1-5 = 1 through 5)
Slash (/): Interval (e.g., */5 = every 5 minutes, 0-23/2 = every 2 hours)

Common Cron Expression Examples

* * * * * → Run every minute
0 * * * * → Run at minute 0 of every hour
0 0 * * * → Run daily at midnight
0 9 * * 1-5 → Run at 9 AM on weekdays (Mon-Fri)
*/15 * * * * → Run every 15 minutes
0 0 1 * * → Run at midnight on the 1st of every month
0 2 * * 0 → Run at 2 AM every Sunday
30 3 15 * * → Run at 3:30 AM on the 15th of every month

Benefits of Using Cron Expression Generator

1. Prevent Syntax Errors

Cron expression syntax is hard to remember and prone to mistakes when written manually. This tool ensures you generate accurate, error-free cron expressions.

2. Visually Intuitive

Complex schedules can be easily configured by simply selecting options for each field. You can set schedules using natural expressions like 'every Monday at 9 AM'.

3. Preview Next Execution Times

See when your generated cron expression will actually execute by viewing the next 5 scheduled run times in real-time. Catch configuration mistakes before deployment.

4. Universal Compatibility

Generated cron expressions work with all cron-compatible systems including Linux crontab, Kubernetes CronJob, GitHub Actions, Docker, AWS EventBridge, and more.

5. Save Time

No need to look up documentation to check cron expression syntax. Use presets to configure common schedules (hourly, daily, weekly, monthly) with a single click.

Cron Expression Tips and Cautions

Be Aware of Timezones

Cron expressions do not contain timezone information. The execution timezone depends on the server's system time or container configuration. For cloud services, you often need to explicitly specify timezone settings (e.g., GitHub Actions uses UTC).

Day and Weekday Combination

When both day field (3rd) and weekday field (5th) are specified, they are treated as OR conditions. Example: '15 10 1 * 1' means 'at 10:15 on the 1st of every month' OR 'at 10:15 every Monday'.

Always Test After Configuration

Before applying to production, we recommend test runs at short intervals (e.g., every minute) to verify expected behavior. Enable log output to track execution history.

Monitor Execution Failures

Always set up notifications for cron job failures (email, Slack, PagerDuty, etc.). This is essential especially for critical operations like backups or payment processing.

Frequently Asked Questions (FAQ)

What is the maximum length for cron expressions?

Standard cron expressions use 5-field format and typically fit within 20 characters. This tool can generate all patterns of 5-field cron expressions. Some systems support 6-field (including seconds) or 7-field (including year) formats, but this tool supports the most widely used 5-field format.

Where can I use the generated cron expressions?

You can use them in any system that supports cron expressions: Linux/Unix crontab, Kubernetes CronJob, GitHub Actions, GitLab CI/CD, AWS EventBridge, Google Cloud Scheduler, Docker (ofelia), Jenkins, CircleCI, and more.

Can I configure 'every Monday and Friday at 9 AM'?

Yes, you can. Select '1,5' (Monday and Friday) in the weekday field, '9' in the hour field, and '0' in the minute field to generate '0 9 * * 1,5'.

How do timezones work with cron expressions?

Cron expressions do not include timezone information. Execution time depends on the system time of the server or container running the task. GitHub Actions uses UTC, AWS uses regional timezones, etc., depending on the platform.

What's the difference between '*/5' and '0-59/5'?

In most cases, they behave the same. Both mean 'every 5 minutes', but '*/5' is more concise and readable, so it's recommended.

How do I specify 'weekdays only' in a cron expression?

Specify '1-5' in the weekday field. This targets Monday through Friday only. Example: '0 9 * * 1-5' means 9 AM on weekdays.

What if next execution times don't display?

If the cron expression is invalid or specifies very rare conditions (e.g., February 30th), next execution times cannot be calculated. Please check your configuration.

Are cron expressions affected by daylight saving time?

Yes, if the server's timezone has daylight saving time enabled, cron execution times will be affected. During DST transitions, tasks may be skipped or run twice. For critical tasks, consider operating in UTC.