How do I test a cron expression online?

Paste your cron expression into PDFFlare's cron expression tester. The tool parses it via cron-parser, converts it to plain English with cronstrue, and shows the next 5-50 fire times in any of 23 timezones. The description updates as you type, so you see immediately whether the expression matches your intent. All parsing runs in your browser — no upload, no signup.

What's the difference between standard cron and Quartz cron?

Standard Unix/Linux cron uses 5 fields: minute, hour, day-of-month, month, day-of-week. Quartz (used by Java schedulers, Spring, and Kubernetes-style 6-field forms) uses 6 or 7 fields by adding seconds at the start and optionally year at the end. PDFFlare's tester accepts all three: paste a 5-field, 6-field-with-seconds, or 7-field-Quartz expression and it parses correctly.

Why does my cron schedule fire at the wrong time?

Almost always a timezone mismatch. Cron expressions don't include a timezone — the schedule interprets them in whatever TZ the runner uses (UTC for most cloud providers like AWS, GCP; the server's local TZ for Linux crontab). Switch the Timezone dropdown in PDFFlare's tester to confirm what time '0 9 * * *' actually fires in your environment. If it fires at 9 AM UTC but you wanted 9 AM Pacific, you need '0 17 * * *' UTC instead.

Does day-of-month and day-of-week combine with AND or OR?

OR — the union, not the intersection. If you write '0 0 1 * 1' (1st of month AND every Monday), the schedule fires on EVERY Monday OR every 1st of the month — both, not just Mondays that fall on the 1st. This is one of the most-misunderstood corners of cron syntax. PDFFlare's plain-English description makes this explicit so you can verify before deploying.

Is Sunday 0 or 7 in cron syntax?

Both. Standard cron treats 0 and 7 identically as Sunday. PDFFlare's tester accepts either. The other common gotcha is that Monday is 1 (not 2), so '0 9 * * 1-5' is Monday-Friday — not Tuesday-Saturday like some assume. The plain-English description renders weekday names so you can confirm at a glance.

What does '*/15' mean in a cron expression?

It's the step operator — '*/15' in the minute field means 'every 15th minute starting at 0', so it fires at :00, :15, :30, :45 every hour. Generally '*/N' means 'every N units'. '5/15' (without the leading *) means 'starting at 5, every 15 units' — fires at :05, :20, :35, :50. The step operator works in any field: '*/2 * * * *' is every 2 minutes, '0 */6 * * *' is every 6 hours, '0 0 */2 * *' is every 2 days.

Can I use this for Kubernetes CronJob expressions?

Yes — Kubernetes uses standard 5-field cron syntax with no seconds field. Paste your CronJob's `spec.schedule` value directly into PDFFlare's cron expression tester to verify it fires when expected. Switch the timezone dropdown to your cluster's TZ (or UTC if you set spec.timeZone) to see the correct next-fire calculation. Useful for debugging CronJobs that aren't firing when expected.

Does the cron tester run offline?

Yes — once the page loads, parsing and next-fire-time computation run entirely in your browser via the cron-parser and cronstrue libraries. No network requests are made during testing. Open DevTools → Network and you'll see zero traffic while you type, switch timezones, or change the result count. Safe for testing schedules from confidential infrastructure or air-gapped environments.

How is this different from `crontab.guru`?

Same general idea — paste cron, get description + next fire times. PDFFlare's tester adds: 23-timezone selector (crontab.guru is always your local TZ); 5/10/25/50 fire-time count toggle; one-click Unix epoch copy for piping into APIs (pairs with PDFFlare's Timestamp Converter); 12 quick presets covering the most common schedules; built-in cron syntax cheatsheet; full Quartz 6-7 field support; dark mode; and runs offline after page load. crontab.guru is excellent for quick checks; PDFFlare's version is built for working through schedules at scale.

What if my expression has special characters like @hourly or @daily?

The shorthand macros (@hourly, @daily, @weekly, @monthly, @yearly, @reboot) are accepted by PDFFlare's parser. They expand to standard 5-field expressions: @hourly = '0 * * * *', @daily = '0 0 * * *', @weekly = '0 0 * * 0', @monthly = '0 0 1 * *', @yearly = '0 0 1 1 *'. @reboot is system-cron specific (fires when cron daemon starts) and can't be modeled as a recurring schedule, so the tester reports it as informational.

Cron Expression Tester Online — Validate + Next Run

Cron expression tester online — paste a cron, get plain-English description and next 50 fire times in any timezone. Free, browser-based.

PDFFlare's cron expression tester parses any cron schedule (standard 5-field, 6-field with seconds, or Quartz 7-field syntax) and shows you exactly what it does — plain-English description plus the next 5-50 fire times in any of 23 timezones. Use it as a cron schedule online debugger, a cron expression generator (paste a preset, edit, copy), a cron next run time calculator for migration planning, or a kubernetes cronjob tester before you apply a CronJob YAML manifest.

Common gotchas the tester surfaces: day-of-month vs day-of-week is OR (not AND); Sunday is both 0 and 7; cron schedules don't include timezone (so ‘0 9 * * *’ fires at 9 AM in whatever TZ the runner uses). Pair with PDFFlare's Timestamp Converter to convert any computed fire time to Unix epoch for pipeline integration, the JWT Decoder for verifying token issued-at and expiration claims, or the UUID Generator for IDs to attach to scheduled job runs.

Acts as a crontab generator, what does this cron run translator, and cron parser online — all in one page. 12 quick presets (every minute, every 5/15 min, hourly, daily 9 AM, weekday 9 AM, weekend midnight, first of month, yearly Jan 1, etc.); 23 timezones; selectable result count; built-in cron syntax cheatsheet. Free, browser-based, no signup, no upload.

Quick presets

Cron expression

Five fields: minute hour day-of-month month day-of-week. Six-field expressions (with seconds prepended) and Quartz syntax (with year appended) are also supported.

Timezone

Number of next fire times

Valid · plain English

Every 15 minutes, between 09:00 AM and 05:59 PM, Monday through Friday

Next 5 fire times · UTC

1Mon, May 11, 2026, 09:00:00 UTC

2Mon, May 11, 2026, 09:15:00 UTC

3Mon, May 11, 2026, 09:30:00 UTC

4Mon, May 11, 2026, 09:45:00 UTC

5Mon, May 11, 2026, 10:00:00 UTC

Cron syntax cheatsheet

┌── minute (0-59)

│ ┌── hour (0-23)

│ │ ┌── day of month (1-31)

│ │ │ ┌── month (1-12 or JAN-DEC)

│ │ │ │ ┌── day of week (0-7 or SUN-SAT)

│ │ │ │ │

* * * * *

* matches every value
*/5 matches every 5th value (0, 5, 10, …)
1-5 matches values 1 through 5 inclusive
1,3,5 matches the listed values
Day-of-week: 0 AND 7 both = Sunday
When BOTH day-of-month AND day-of-week are specified, the schedule fires on EITHER (OR, not AND)

Parsing runs entirely in your browser via cron-parser + cronstrue. Nothing is uploaded. Timezone + result-count preferences persist across reload via localStorage.

How to Test a Cron Expression

Paste a cron expression or pick a preset
Type or paste your cron expression in the input — standard 5-field syntax (minute hour day-of-month month day-of-week), 6-field with seconds prepended, or Quartz syntax with year appended. Or click a preset like 'Every 15 minutes' or 'Weekday 9 AM' to populate the field instantly.
Read the plain-English description
PDFFlare parses the expression and shows what it actually means in regular sentences. 'Every 15 minutes, between 9:00 AM and 5:59 PM, Monday through Friday' is much easier to verify than '*/15 9-17 * * 1-5'. The description updates as you type.
Verify the next fire times
See the next 5, 10, 25, or 50 times the schedule will fire — in any of 23 timezones. Each row shows the absolute timestamp + a relative-time hint ('in 2 hours', 'tomorrow') and a one-click Epoch copy for piping into APIs that expect Unix timestamps.
Switch timezones if needed
Cron expressions are timezone-aware: the same '0 0 * * *' fires at midnight UTC vs midnight America/New_York vs midnight Asia/Tokyo. Switch the Timezone dropdown to preview when your cron actually runs in your target region. Useful when debugging schedules on remote servers.

When Do You Need a Cron Expression Tester?

Verifying a Kubernetes CronJob before kubectl apply: CronJob manifests use 5-field cron syntax. Wrong schedule ships, fires every minute on production, and floods your logs. Paste the schedule into PDFFlare's cron expression tester before applying — confirm both the plain-English description AND the next 5 fire times match your intent.

Debugging a cron job that fires at the wrong time: Almost always a timezone mismatch — your laptop is in America/Los_Angeles but the cron runs on a UTC server. Switch the Timezone dropdown to UTC, see what the schedule actually fires at, and adjust accordingly. Pairs cleanly with PDFFlare's Timestamp Converter for converting fire-times to Unix epoch.

Reading a cron expression you didn't write: An on-call alert fires from a 5-year-old cron job. You need to know what it does NOW, not parse it manually. Paste, get plain English, decide whether to silence the alert or fix the underlying job. Cuts the “wait what does this run” tax from minutes to seconds.

Building a new schedule from a vague requirement: The PM said “run every weekday morning around 9.” You write “0 9 * * 1-5” and want to verify before deploying. The tester confirms it fires Monday-Friday at 9:00 AM exactly, and shows you the next 5 fire times so you can see whether your start window looks right. Quick presets cover the most common schedules so you don't have to write from scratch.

Why Use PDFFlare's Cron Expression Tester?

Plain-English + Next Fire Times

Verify your schedule two different ways: read the English description (“every 15 minutes, weekdays, between 9 AM and 5:59 PM”) AND see the next 5-50 actual fire times. Catches both syntax bugs and timezone-mismatch bugs.

Standard, 6-Field, and Quartz Support

Linux crontab, GitHub Actions, AWS EventBridge, Kubernetes CronJob (5-field), Spring/Quartz Java schedulers (6-7 field with seconds + year). Same tester, every common syntax. @hourly / @daily / @weekly / @monthly / @yearly macros also work.

100% Browser-Based

Parsing via cron-parser + cronstrue, both running client-side. Nothing is uploaded. Open DevTools → Network and you'll see zero requests during testing. Safe for confidential schedules from production infrastructure.

No Signup Required

Free, unlimited, no account, no rate limits. 12 quick presets, 23 timezones, selectable 5/10/25/50 result counts, one-click Unix epoch copy on every fire time, built-in cron syntax cheatsheet.

Frequently Asked Questions About Cron Expression Tester

Password Generator

Random, passphrase, PIN

UUID Generator

v1, v4, v5, v7 + bulk

HMAC Generator

HMAC-SHA256 webhook signatures

File Checksum

MD5 + SHA hashes of any file

Verify Checksum

Match a published hash to a file

Random Secret

JWT secrets, API keys, webhook keys