Free Cron Expression Generator & Explainer

Build, parse and explain standard 5-field cron / crontab schedules in your browser. Plain-English descriptions, presets, a simple builder, and next-run previews in your timezone. 100% client-side: expressions are never sent, logged, or put in the URL.

🔒 Parsed in your browser · Never sent or stored · Never written to the URL · Works offline · Free, no sign-up

Presets

Timezone

Cron expression

minute · hour · day-of-month · month · day-of-week

Human description

At 09:00 on Monday through Friday

Next runs

Enter a valid expression to preview the next fire times.

How to build a cron expression

Paste or build an expression

Type a 5-field cron, tap a preset, or use the simple builder controls.

Read the plain-English explanation

Cronly turns the schedule into a clear human description (and Traditional Chinese on /zh).

Pick a timezone

Default Asia/Hong_Kong, plus UTC and other common zones via Intl.

Preview next runs

See the next ~10 fire times. Copy the expression — nothing is uploaded or put in the URL.

A crontab tool that never sees your schedules

Cronly runs entirely in your browser. Paste a 5-field cron expression to get a plain-language explanation and the next fire times in your chosen IANA timezone (via Intl). Use presets or the builder for common patterns such as every 15 minutes, weekdays at 09:00, or the 1st of the month. Nothing is sent to a server, nothing is logged, and the expression is never placed in the URL.

Features

5-field cron parser with clear validation errors
Plain-English schedule explanations
Presets + simple builder for common patterns
Next ~10 runs in your timezone — nothing uploaded or put in the URL

Why Cronly?

🚫 Explained on your device: expressions are never sent, logged or stored
🧩 Zero-dep custom parser — no heavy cron libraries
🛡️ Never written to the URL, so history and analytics stay clean
🆓 Free, no sign-up, no limits, works offline after the page loads

All ToolBookly tools · Epochly · JSONly · Passly · Jwtly

Frequently Asked Questions

Are cron expressions sent to a server?

No. Cronly parses, explains, and previews cron schedules entirely in your browser. Expressions are never uploaded, logged, or written into the page URL. Once the page has loaded it even works offline.

Which cron format does Cronly use?

Standard 5-field cron: minute, hour, day-of-month, month, day-of-week (in that order). Values support *, ranges (1-5), lists (1,15), and steps (*/15). Day-of-week 0 and 7 both mean Sunday. Month and weekday name aliases (jan, mon, …) are accepted.

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

When both fields are restricted (not *), Cronly follows classic cron OR semantics: the job fires when either the day-of-month or the day-of-week matches. If only one field is restricted, that field alone is required.

How are next run times calculated?

Cronly walks the schedule in your chosen IANA timezone using the browser’s Intl API (including daylight saving). It shows the next ~10 fire times from “now”. No heavy cron libraries.

Why is there no share link with my expression?

Schedules can reveal internal job timing. Cronly deliberately never puts the expression into the query string or hash, so copied links cannot leak it into history or analytics. Use the Copy button instead.

Is Cronly free?

Yes. Free, no sign-up, no limits. It is part of the ToolBookly suite of browser tools.