voiddo cronwtf vs crontab.guru
Both translate cron expressions into human language. This page compares what each does, where they differ, and when to reach for each one.
voiddo cronwtf — use when
- You want the next 5 actual run timestamps in your local timezone
- You need to verify a Jenkins or Quartz 6-field cron (with seconds)
- You want to paste and get a result fast — no field-by-field editing
- You need no ads, no account, and zero data sent to a server
- You want to understand what a cron string does right now
crontab.guru — use when
- You are building a cron expression field by field interactively
- You want per-field highlighting to understand each position
- You want a schedule visualizer (calendar view of runs)
- You prefer the minimal, iconic UI that many developers know
feature comparison
| feature | voiddo cronwtf | crontab.guru |
|---|---|---|
| plain English description | ✓ | ✓ |
| next run timestamps | ✓ next 5 in your local timezone | ✓ next run (UTC) |
| local timezone display | ✓ auto-detects browser timezone | UTC only |
| Jenkins / Quartz 6-field (seconds) | ✓ auto-detected | 5-field only |
| @daily @hourly shorthands | ✓ | ✓ |
| per-field visual editor | paste-and-translate only | ✓ interactive field editor |
| calendar schedule visualizer | – | ✓ |
| runs in browser (no server call) | ✓ | ✓ |
| ads | none | none |
| account required | no | no |
| price | free | free |
frequently asked questions
Is cronwtf a crontab.guru alternative?
Yes, for translation tasks. cronwtf focuses on a different workflow: you paste an existing cron string and instantly get the plain-English description plus the next 5 fire times in your local timezone. crontab.guru is better when you are composing a cron expression from scratch and want visual feedback on each field. Both are free and browser-based.
What is Jenkins or Quartz cron syntax?
Standard 5-field cron is:
minute hour day-of-month month day-of-week. Jenkins and Quartz add a seconds field at the beginning, giving 6 fields: second minute hour day-of-month month day-of-week. For example, 30 0 9 * * MON-FRI means "every weekday at 09:00:30". Many standard cron parsers reject 6-field input with "invalid expression". cronwtf auto-detects whether you have 5 or 6 fields and parses both.Why does my cron job run at the wrong time?
Almost always a timezone mismatch. Cron expressions contain no timezone information — they fire at the server's local time. Most Linux servers run UTC. If your server is UTC and you expected
0 9 * * * to run at 9 AM Jerusalem time (IDT, UTC+3), it will actually run at 9 AM UTC which is noon IDT. cronwtf shows the next 5 runs in your browser's local timezone so you can immediately see if the offset is correct.What does @reboot, @daily, @hourly mean in cron?
@reboot: run once when the system starts. @hourly: equivalent to 0 * * * * (top of every hour). @daily and @midnight: both mean 0 0 * * * (once a day at midnight). @weekly: 0 0 * * 0 (Sunday midnight). @monthly: 0 0 1 * * (first of each month). @yearly and @annually: 0 0 1 1 * (January 1st). cronwtf parses all these shorthands and translates them.Can I use cron to run a job every 30 seconds?
Standard 5-field cron has a 1-minute minimum interval. To run every 30 seconds with standard cron you need two entries:
* * * * * /your/script and * * * * * sleep 30 && /your/script. Jenkins/Quartz 6-field cron supports 0/30 * * * * * (every 30 seconds). For truly sub-minute jobs, systemd timers or application-level scheduling is more robust than cron.