Stop memorizing asterisk syntax. Build complex Linux cron schedules visually and generate perfect crontab commands for your server automation scripts.
0 * * * *every hour, at minute 0
Use * for any value, */n for every n, a-b for ranges, a,b for lists
A single typo in a crontab file can accidentally run a database backup every minute instead of every month, crashing your server.
Select your schedule using simple, human-readable dropdowns ("Every Friday at 2:30 AM"). The generator handles the complex modulo math instantly.
Easily configure advanced syntax like `*/15` to trigger a script every 15 minutes without writing out massive, error-prone comma-separated lists.
The output isn't just the asterisks. Add your script path into the tool, and it outputs the entire string ready to be copy-pasted into `crontab -e`.
Cron is a background daemon on Unix-like operating systems (Linux, macOS) that acts as a time-based job scheduler. System administrators use cron to schedule scripts to execute automatically at specific intervals—such as running database backups at midnight, clearing server logs every Sunday, or sending marketing emails.
A "cron job" is defined within a configuration file called a crontab (Cron Table). Because cron was invented in 1975 to be highly memory-efficient on legacy mainframes, it does not use human-readable words. Instead, it uses a strict sequence of 5 fields separated by spaces, followed by the command to execute.
The asterisk (*) is not a wildcard; it specifically means "every".
A very common junior developer mistake is wanting a script to run "Every Tuesday". They will generate a string like this: * * * * 2. However, because the first field (Minute) is an asterisk, this command actually says: "Run every minute, of every hour, of every day, of every month, but only if it's a Tuesday." The script will run 1,440 times in one day, likely crashing the server.
To run a script just once on Tuesday (e.g., at 5:00 AM), the correct syntax is 0 5 * * 2. Using a visual Crontab Generator prevents these catastrophic logic errors by visually confirming exactly when the job will execute.
If you want a script to run multiple times, you do not need to create multiple crontab lines. Cron supports advanced mathematical operators:
0 15,18 * * * will run the script at exactly 15:00 (3 PM) and 18:00 (6 PM) every day.0 9-17 * * 1-5 will run the script at the top of every hour from 9 AM to 5 PM, but only Monday through Friday (business hours).*/15 * * * * is a division operator. It means "Run on every minute that is divisible by 15" (e.g., :00, :15, :30, :45).Cron executes jobs in a restricted, non-interactive shell environment. This means cron does not load your user's .bashrc or system PATH variables. If your cron job command is simply node script.js, it will silently fail because cron has no idea where "node" is installed. You must always use absolute paths in your crontab, for example: /usr/bin/node /var/www/project/script.js.