Cron Expression Validator
DataValidate cron expressions for standard 5-field and 6-field (with seconds) formats. Checks ranges, step values, and special chars like L, W, and #. Instant.
What is a Cron?
The Cron Expression Validator checks whether a cron expression follows correct syntax — validating each field against its allowed range, verifying that special characters are used in the right positions, and providing a plain-English description of what the schedule does.
Cron expressions are the standard way to define recurring schedules in Unix/Linux systems, CI/CD platforms, cloud schedulers (AWS EventBridge, Google Cloud Scheduler), and application frameworks (Spring, Quartz). A valid cron expression looks deceptively simple — five space-separated fields — but the rules for each field are distinct, and several extended special characters (L, W, #, ?) are only legal in specific positions.
This validator supports both the 5-field standard Unix format and the 6-field format that prepends a seconds field (used by Quartz, Spring, and some cloud platforms). It handles all standard special characters (*, ,, -, /) and the Quartz extensions (L, W, #, ?). Auto-detect is on by default — the validator infers 5 or 6 fields from the expression itself.
Use this alongside the Regex Tester and Date Validator for related developer-tooling tasks.
How to use this Cron calculator
- Type or paste the cron expression into the input field (e.g.
*/5 * * * *or0 9 * * 1-5). - Select a format from the dropdown — Auto-detect (default) works for most cases; use 5-field or 6-field explicitly if needed.
- The result updates automatically as you type.
- Check the Valid or Invalid badge.
- If Invalid, read the error message — it will name the field and the specific rule that failed.
- If Valid, check the details section for the field breakdown and plain-English schedule description.
Formula & Methodology
5-field format:minute hour day-of-month month day-of-week6-field format (Quartz/Spring):second minute hour day-of-month month day-of-weekField ranges: | Field | Range | Named aliases | |---|---|---| | Second | 0–59 | — | | Minute | 0–59 | — | | Hour | 0–23 | — | | Day-of-month | 1–31 | — | | Month | 1–12 | JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC | | Day-of-week | 0–7 | SUN MON TUE WED THU FRI SAT (0 and 7 both = Sunday) | Special characters and where they are valid: | Char | Meaning | Valid fields | |---|---|---| |*| Every value | All | |,| List (e.g.1,3,5) | All | |-| Range (e.g.1-5) | All | |/| Step (e.g.*/5,1-30/2) | All | |?| No specific value | day-of-month, day-of-week | |L| Last (day of month or last weekday of type) | day-of-month, day-of-week | |W| Nearest weekday | day-of-month only | |#| Nth weekday in month (e.g.2#3= 3rd Monday) | day-of-week only | Valid examples: -* * * * *— every minute -0 9 * * 1-5— 9am on weekdays (Mon–Fri) -*/15 * * * *— every 15 minutes -0 0 L * ?— midnight on the last day of each month (Quartz) -0 0 ? * 2#1— midnight on the first Monday of each month (Quartz) Invalid examples: -* * * * 8— day-of-week 8 is out of range (0–7) -*/0 * * * *— step value of 0 is not allowed -60 * * * *— minute 60 is out of range (0–59) -0 9 L * *—Lis not valid in the month field -30-10 * * * *— range start (30) must be ≤ range end (10)
Frequently Asked Questions
What is a cron expression?
A cron expression is a string of 5 (or 6) space-separated fields that defines a schedule for a recurring task. It is used by the cron daemon on Unix/Linux systems, as well as by task schedulers in cloud services (AWS EventBridge, Google Cloud Scheduler, GitHub Actions), CI/CD platforms, and application frameworks. The expression specifies when a job should run by encoding the minute, hour, day of month, month, and day of week.
What are the 5 fields in a standard cron expression?
The five fields are, in order: minute (0–59), hour (0–23), day-of-month (1–31), month (1–12 or JAN–DEC), and day-of-week (0–7, where both 0 and 7 represent Sunday, or SUN–SAT). For example, '30 9 * * 1' means 'at 09:30 every Monday'. A '*' in a field means 'every value in that field's range'.
What is the difference between 5-field and 6-field cron expressions?
Standard Unix cron uses 5 fields (minute through day-of-week). Some schedulers — including Spring Framework's @Scheduled, Quartz Scheduler, and several cloud platforms — prepend a second field, making it a 6-field expression. The 6-field format is: second (0–59), minute (0–59), hour (0–23), day-of-month (1–31), month (1–12), day-of-week (0–7). The validator supports both and can auto-detect which format you are using based on the number of fields.
What does the '/' character do in a cron expression?
The '/' character defines a step value. '*/5' in the minute field means 'every 5 minutes'. '10/15' means 'starting at minute 10, then every 15 minutes' (i.e., 10, 25, 40, 55). A range with a step like '0-30/5' means every 5 minutes between 0 and 30 (0, 5, 10, 15, 20, 25, 30). The step value must be at least 1.
What does 'L' mean in a cron expression?
L stands for 'last'. In the day-of-month field, 'L' alone means the last day of the month (28, 29, 30, or 31 depending on the month). 'L-3' means three days before the last day of the month. In the day-of-week field, '5L' means the last Friday of the month. 'LW' in day-of-month means the last weekday of the month. L is supported in Quartz-compatible schedulers but not in standard Unix cron.
What does '#' mean in a cron expression?
The '#' character means 'nth occurrence of a weekday in the month'. It is only valid in the day-of-week field. For example, '2#3' means the third Monday of the month (2 = Monday, 3 = third occurrence). '6#1' means the first Saturday. Values for the nth position must be 1–5. This is a Quartz extension and is not supported by standard Unix cron.
What does 'W' mean in a cron expression?
W means 'nearest weekday' and is only valid in the day-of-month field. '15W' means 'the nearest weekday to the 15th of the month'. If the 15th is a Saturday, the job runs on the 14th (Friday). If it is a Sunday, the job runs on the 16th (Monday). 'W' is a Quartz extension and is not available in standard Unix cron or most simple schedulers.
What does '?' mean in a cron expression?
The '?' character means 'no specific value' and is only valid in the day-of-month and day-of-week fields. It is used when you want to specify one of these fields but not the other — for example, '0 12 15 * ?' means noon on the 15th of every month, regardless of which day of the week that falls on. Using '*' in both dom and dow would be ambiguous in some schedulers; '?' resolves that ambiguity. Standard Unix cron does not use '?'.
Why would a cron expression work on one platform but fail on another?
Different schedulers support different subsets of cron syntax. Standard Unix cron (used in /etc/crontab and crontab -e) supports only the 5 basic fields and the * , - / special characters. Quartz Scheduler (Java) adds the L, W, #, and ? extensions and uses a 6-field format with seconds. AWS EventBridge uses a 6-field format with years instead of seconds. GitHub Actions uses standard 5-field Unix cron. This validator flags the specific extension characters so you know what each platform does or does not support.
Is my cron expression stored when I use this tool?
No. All validation runs in your browser. The expression you enter is never transmitted to any server, stored in a database, or shared with any third party.
What are some common cron expression examples?
Here are frequently used patterns: '* * * * *' runs every minute. '0 * * * *' runs at the top of every hour. '0 0 * * *' runs at midnight every day. '0 9 * * 1-5' runs at 9am on weekdays. '*/15 * * * *' runs every 15 minutes. '0 0 1 * *' runs at midnight on the first of every month. '0 0 * * 0' runs at midnight every Sunday.