What does a cron expression with five fields mean?

The five fields, in order, are minute (0–59), hour (0–23), day of month (1–31), month (1–12), and day of week (0–6, where 0 is Sunday). A value of * means “every” for that field.

How do I write a cron job that runs every 15 minutes?

Use */15 in the minute field and * for the rest: */15 * * * *. The */15 is a step value meaning “every 15th minute starting at 0,” so it fires at :00, :15, :30, and :45.

What is the cron expression for every day at midnight?

0 0 * * * runs once a day at 00:00. The first 0 is minute zero and the second 0 is hour zero (midnight).

Does Cron Builder support seconds or non-standard cron?

Standard Unix cron uses five fields and does not include seconds. Some schedulers (like Quartz or certain Kubernetes setups) add a seconds field or special characters; check your scheduler's documentation if your expression has six fields.

Is my cron expression sent to a server?

No. Cron Builder runs entirely in your browser. Expressions are parsed and previewed locally, so nothing you type is transmitted or stored on a server.

Cron Builder

Create and read cron expressions with human-friendly previews. Build expressions visually or paste one to understand it.

Paste & Explain

Enter a standard 5-field cron expression.

Cron Expression

Description

Enter a valid expression above...

Next Predicted Run Times

Enter a valid expression above...

Times shown in your browser's local time zone. Time zone support not yet implemented.

About Cron Builder

A cron expression is a compact, five-field string that tells a scheduler exactly when to run a job — minute, hour, day of month, month, and day of week. The syntax is powerful but unforgiving: a single misplaced asterisk can turn “every Monday at 9am” into “every minute,” and the only feedback you usually get is a job that fired ten thousand times overnight.

Cron Builder removes the guesswork. Build an expression visually by picking values for each field and watch a plain-English description update live, or paste an existing expression to instantly understand what it does and when it will next run. Everything runs in your browser — no expression ever leaves your device — so it's safe to drop in production schedules from your own infrastructure.

It's built for the moments you reach for cron under pressure: wiring up a backup at 2am, a cache warm every fifteen minutes, or a report on the first business day of the month. Get the timing right the first time instead of decoding it from logs.

How to use Cron Builder

Choose a field to edit
Start with the minute field and work across to day-of-week. Each field offers presets (every, specific values, ranges, steps) so you don't have to remember the raw syntax.
Read the live description
As you adjust fields, a human-readable summary updates in real time — for example “At 09:00 on Monday.” Use it to confirm the schedule matches your intent.
Check the next run times
Preview the upcoming execution timestamps to catch off-by-one mistakes (like a job firing daily when you meant weekly) before you ship.
Copy the expression
Copy the finished cron string into your crontab, CI pipeline, Kubernetes CronJob, or scheduler of choice.

Frequently asked questions

Timestamp Converter

Convert Unix timestamps (seconds/ms), ISO 8601 strings, and human-readable dates. View local time, relative time, and next cron times.

UUID Generator & Validator

Generate v1 or v4 UUIDs, validate existing ones, detect versions, and inspect v1 timestamps.

Regex Highlighter

Highlight matching text in real-time using your custom regular expressions.