Cron Expression Parser
Parse a standard 5-field cron expression into a plain-English description and see the next 5 run times. Validates fields, supports *, */n, ranges and lists, and runs entirely in your browser.
Common Presets
Tap to load a schedule
Supports *, */n, ranges a-b and lists a,b,c.
How to use this tool
Enter Your Expression
Type or paste a five-field cron expression (minute hour day-of-month month day-of-week), or tap a common preset.
Read It In Plain English
See an instant human-readable description of when the job fires, with any invalid field flagged clearly.
Preview Upcoming Runs
Check the next 5 run datetimes computed from your local clock to confirm the schedule before deploying.
Remember that when both day-of-month and day-of-week are set, classic cron runs when EITHER matches — the next-run preview reflects this so you can verify it.
Five space-separated fields. Runs entirely in your browser — nothing is uploaded.
- 1Thu Jan 01 1970 — 09:00
- 2Fri Jan 02 1970 — 09:00
- 3Mon Jan 05 1970 — 09:00
- 4Tue Jan 06 1970 — 09:00
- 5Wed Jan 07 1970 — 09:00
Why It Helps
A misread cron field can silently break a backup or fire a job thousands of times. Seeing the next run times confirms your schedule does exactly what you intend before you commit it to a crontab or CI pipeline.
Turn Cryptic Crontab Lines Into Clear Schedules
Cron expressions are compact but easy to misread, and a single wrong digit can mean a backup never runs or a job fires every minute instead of every hour. This cron expression parser takes a standard five-field schedule, explains it in plain English, and shows you the next five times it will actually run — all instantly, as you type. It is built for developers, SREs and anyone editing a crontab or a CI schedule who wants to confirm their intent before shipping.
What the Tool Does
You paste a five-field expression — minute hour day-of-month month day-of-week — and the parser does three things. First it validates every field against its legal range and syntax. Then it generates a human-readable description such as "At 09:00 on Monday, Tuesday, Wednesday, Thursday, Friday." Finally it computes the next five run datetimes by stepping forward from the current minute on your device, so you can see concrete dates rather than abstract rules.
A Worked Example
Take the expression 30 8 * * 1-5. Reading the fields in order:
- minute = 30 — at the 30-minute mark
- hour = 8 — during the 8 o'clock hour
- day-of-month = * — any day of the month
- month = * — any month
- day-of-week = 1-5 — Monday through Friday
Put together, that is "At 08:30 on Monday, Tuesday, Wednesday, Thursday, Friday" — a classic weekday morning job. The parser then lists the next five matching weekday mornings from right now, so if today is a Saturday you will see the upcoming Monday first. Change 1-5 to 1,3,5 and the schedule instantly becomes Monday, Wednesday and Friday only; change 30 8 to */30 8 and it fires at both 08:00 and 08:30.
The Syntax It Supports
The tool covers the four operators you will meet in almost every crontab:
*— every value in the field*/n— a step, e.g.*/15in the minute field means every quarter houra-b— an inclusive range, e.g.9-17for business hoursa,b,c— an explicit list of values
These can be mixed inside one field, so 0,15,30,45 9-17 * * 1-5 is fully valid and describes "every 15 minutes during business hours on weekdays."
When Developers Reach For It
Cron parsing comes up constantly: reviewing a teammate's pull request that touches a scheduler, debugging why a nightly report arrived at the wrong time, migrating jobs between servers in different timezones, or simply double-checking a schedule you wrote months ago. Because the next-run preview uses your local clock, it is also a quick way to reason about timezone offsets before a deploy. The classic gotcha — that day-of-month and day-of-week combine with OR logic when both are set — is handled for you, so the run times you see match how real cron daemons behave.
Private and Instant
Everything runs in your browser with plain JavaScript. Your expressions never leave your device, which matters when the schedules come from internal infrastructure. There is no signup, no rate limit, and it keeps working offline once the page has loaded.
Pair It With Other Tools
Cleaning up a config file or documentation alongside your schedules? Run prose through the word & character counter to hit length limits, or normalise labels and slugs with the text case converter before committing.