What does "*/15 * * * *" mean?

It means "every 15 minutes". The */n pattern in a field means "every nth value of that field" — so */15 in the minute field fires at minute 0, 15, 30, and 45 of every hour.

Is any data sent to a server?

No. All parsing and translation runs locally in your browser using JavaScript. Nothing is sent to any server.

Does this support 6-field cron (with seconds)?

This tool covers the standard 5-field POSIX cron used by crontab, GitHub Actions, Railway, Heroku Scheduler, AWS EventBridge, and most CI/CD tools. 6-field formats (with a leading seconds field) are used by some frameworks like Spring — enter the 5 fields that correspond to minute through day-of-week.

What are the five cron fields and their ranges?

In order: 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 in a field means "every" value of that field.

What does a range like 1-5 mean in the day-of-week field?

It means every value from the first to the last inclusive. In the day-of-week field 1-5 is Monday through Friday, so "0 9 * * 1-5" runs at 09:00 on weekdays.

How do comma lists work, for example "0 0,12 * * *"?

A comma list fires on each listed value. "0 0,12 * * *" runs at minute 0 of hour 0 and hour 12 — i.e. at midnight and noon every day.

What happens when both day-of-month and day-of-week are set?

In standard cron, if both the day-of-month and day-of-week fields are restricted (not *), the job runs when EITHER matches, not both. This is a common source of surprise, so the explainer spells out the day rule in plain English.

What is the Cron Expression Explainer?

Free cron expression explainer and builder. Paste a 5-field cron expression and get an instant plain-English description. Use presets or build from scratch. Supports */n steps, ranges, and comma lists. Runs entirely in your browser — nothing sent to any server. It runs free in your browser on Gera Tools, with nothing uploaded.

Cron Expression Explainer

Name: Cron Expression Explainer
Creator: Gera Tools
License: https://creativecommons.org/licenses/by/4.0/

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Cron expression explainer and builder

This tool translates any 5-field cron expression into a plain-English sentence and breaks each field down so you can spot mistakes at a glance. It’s for anyone scheduling a job in crontab, GitHub Actions, Railway, AWS EventBridge, or a CI pipeline who wants to confirm a schedule reads the way they intended before shipping it.

How it works

A cron expression has five space-separated fields: minute, hour, day-of-month, month, day-of-week. The tool splits on whitespace, validates each field against its allowed range, and translates it. It understands * (every value), */n steps (every nth value), x/n (every nth value starting at x), a-b ranges, and a,b,c comma lists. It then assembles the parsed parts into one sentence — taking care with the cron rule that when both day-of-month and day-of-week are set, the job runs when either matches. Eight presets seed common schedules.

Example expressions explained

The expression:

30 8 * * 1-5

explains as: at 08:30, Monday through Friday. Field by field — minute 30, hour 8, every day of the month, every month, days Monday–Friday. This is the pattern you would use for a weekday morning report or a business-hours job.

A few more common patterns:

0 */4 * * *        →  every 4 hours (at minute 0)
0 0 1 * *          →  at midnight on the 1st of every month
15 14 1 * *        →  at 14:15 on the 1st of every month
0 22 * * 1-5       →  at 22:00 on weekdays

The day-of-month and day-of-week OR trap

A well-known cron surprise: if you restrict both the day-of-month and day-of-week fields, the daemon treats them as an OR. The expression 0 9 15 * 1 fires at 09:00 on the 15th of every month and at 09:00 every Monday — not just on Mondays that happen to fall on the 15th. If you want the second Monday of the month, cron cannot express that directly; you need a wrapper script. The explainer calls this out in the translation so you do not ship the wrong schedule by accident.

Field reference

Field	Position	Range	`*` means
Minute	1	0–59	every minute
Hour	2	0–23	every hour
Day of month	3	1–31	every day
Month	4	1–12	every month
Day of week	5	0–6 (0 = Sun)	every weekday

Where cron expressions run

The standard 5-field format is accepted by crontab on Linux and macOS, GitHub Actions schedules, AWS EventBridge, Railway’s cron service, Heroku Scheduler, and most CI/CD platforms. Tools like Quartz (Java) and some Node.js libraries add a 6th field for seconds — this explainer covers the 5-field POSIX format. All parsing runs locally in your browser — nothing is sent to any server.