What do the five cron fields mean?

In order they 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). An asterisk means every value for that field.

What is the difference between */5 and 5 in the minute field?

*/5 means every 5 minutes (0, 5, 10 …), a step. A plain 5 means only at minute 5 of the hour. Use commas for a list (0,30) and a hyphen for a range (0-15).

Is my cron expression sent anywhere?

No. The builder, validation and the plain-English summary all run entirely in your browser. Nothing you type is uploaded.

Crontab Expression Builder

Build and read cron schedules field by field.

Crontab expression builder

Build a five-field cron schedule one field at a time — minute, hour, day of month, month and day of week — or start from a preset like every 5 minutes or every Monday at 9am. Each field accepts * for any, lists (1,15), ranges (1-5) and steps (*/5).

The cron expression and a plain-English summary update as you type, and the builder flags out-of-range values. Everything runs in your browser; nothing is uploaded.