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Cron Expression Parser Parse and explain cron expressions in plain English with field breakdown and next runs.

Cron Expression Parser illustration
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Cron Expression Parser

Parse and explain cron expressions in plain English with field breakdown and next runs.

1

Paste Expression

Enter any 5-field cron expression.

2

Read Explanation

See the plain English description of the schedule.

3

Verify Runs

Check the next 5 scheduled executions to confirm understanding.

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What Is Cron Expression Parser?

The Cron Expression Parser takes any standard 5-field cron expression and translates it into plain English, making it easy to understand complex scheduling rules at a glance. Paste a cron expression and instantly see a human-readable summary, a field-by-field breakdown showing what each value means, and the next 5 scheduled execution times. The parser handles all standard cron syntax including wildcards (*), step values (*/n), ranges (a-b), and comma-separated lists (a,b,c). Quick-access buttons provide common expressions for fast testing. This is the perfect companion to the Cron Expression Generator — one builds, the other explains.

Why Use Cron Expression Parser?

  • Instant plain English translation of any cron expression
  • Field-by-field breakdown with value ranges
  • Next 5 runs preview for verification
  • Handles all standard cron syntax
  • Quick-access example expressions
  • Essential for code review and documentation

Common Use Cases

Code Review

Quickly understand cron schedules during code reviews without memorizing syntax.

Debugging

Verify that a cron expression triggers at the expected times.

Documentation

Generate human-readable schedule descriptions for technical documentation.

Onboarding

Help new team members understand existing scheduled tasks.

Audit

Review and verify cron schedules across systems during security audits.

Technical Guide

The parser splits the input string on whitespace and validates that exactly 5 fields are present. Each field is analyzed independently to determine its type: wildcard (*), step (*/n), range (a-b), list (a,b,c), or specific value (n). The explainField() function translates each field into natural language, using lookup arrays for day and month names. The summary builder combines field explanations into a coherent sentence, using special-case logic for common patterns (e.g., "1-5" in day-of-week becomes "on weekdays"). The next-run calculator reuses the same minute-by-minute iteration approach as the generator, testing each field with a matchesField() function.

Tips & Best Practices

  • 1
    Use the quick-access buttons to familiarize yourself with common patterns
  • 2
    Always check the "Next 5 Runs" to verify your understanding of the expression
  • 3
    If you're unsure about an inherited cron job, paste it here before modifying
  • 4
    The field breakdown shows the valid range for each position
  • 5
    Pair with the Cron Expression Generator to build and verify in one workflow

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Frequently Asked Questions

Q What cron formats are supported?
Standard 5-field cron (minute, hour, day-of-month, month, day-of-week). 6-field and 7-field variants (with seconds or year) are not currently supported.
Q Can it handle cron expressions from any system?
It handles standard POSIX cron syntax which is compatible with most systems (Linux cron, AWS CloudWatch, GitHub Actions schedule, etc.).
Q What if my expression is invalid?
The parser shows an error message for expressions that don't have exactly 5 fields. Individual field validation may be added in a future update.
Q Is the "Next 5 Runs" based on my local time?
Yes, the next runs are calculated from the current time in your local timezone.
Q Can I parse expressions with names like JAN, MON?
Currently the parser works best with numeric values. Name-based values may not be parsed correctly in all cases.

About This Tool

Cron Expression Parser is a free online tool by FreeToolkit.ai. All processing happens directly in your browser — your data never leaves your device. No registration or installation required.