Cron Expression Validator API

Validate, parse, and preview cron schedules via a simple HTTP API. Built for CI/CD pipelines, monitoring dashboards, and developer tools.

Try it — enter a cron expression:

Click "Validate" to see the analysis.

Features

Impossible Schedule Detection

Catches "Feb 31st", OR-semantics surprises, leap-year traps, and midnight contention spikes.

Human-Readable Descriptions

"At minute 0 past every hour" — clear English descriptions for every valid expression.

Next Run Calculator

Get the next N execution times as ISO timestamps with relative offsets.

Frequency Analysis

Estimate runs per year and detect over-scheduling (every-minute alerts).

API Documentation

# Parse and describe a cron expression (FREE)
GET /api/cron?expr=*/5 * * * *

# Deep validation with insights (FREE)
GET /api/cron/validate?expr=0 0 31 2 *

# Get next N run times (FREE: 5, PRO: up to 100)
GET /api/cron/next?expr=*/5 * * * *&count=20

# Preset library (FREE)
GET /api/cron/presets

Example with curl:

# Parse
curl "https://cronapi.vercel.app/api/cron?expr=*/5 * * * *"

# Validate with Pro key
curl -H "Authorization: Bearer YOUR_KEY" \
  "https://cronapi.vercel.app/api/cron/validate?expr=0 0 31 2 *"

Pricing

Free

100 requests/hour
Parse + describe
Next 5 runs
Validation insights
Preset library

Pro

$5/mo

Unlimited requests
Up to 100 next runs
Batch validation (coming)
Priority support
No rate limits

Get Pro — $5/mo

Use Cases

CI/CD Validation

Validate cron expressions in config files before deploy. Catch impossible schedules in your pipeline.

Monitoring Dashboards

Show human-readable cron descriptions next to scheduled jobs in your observability tools.

Developer Tools

Power cron builders, generators, and validators in your own apps without shipping a parser.

Documentation

Auto-generate descriptions for cron schedules in your docs, runbooks, and architecture diagrams.