Illustration of a cron expression 0 9 * * 1-5 next to a clock, with a plain-English explanation reading runs weekdays at 9 AM

Cron Expression Builder

Type or paste a 5-field cron expression below, or use a preset — the explanation updates live. Runs entirely in your browser.

Build from individual fields instead

ℹ️ Cron syntax reference
  • Five fields, in order: 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, both 0 and 7 mean Sunday).
  • * means "every value"; */N means "every N units"; A-B is a range; A-B/N is a stepped range; A,B,C is a list — these can combine, e.g. 1-5,10-15/2.
  • Runs entirely client-side — nothing you type here is ever sent anywhere. The JSON API below is a separate, opt-in endpoint for scripts.
💻 Show API usage example (cURL)
curl -sS "https://devops.majbase.com/cron-builder/api" \
    --data-urlencode 'cron=0 9 * * 1-5' \
    --data-urlencode 'count=5'

Returns JSON: {"summary": "..."|null, "breakdown": {"minute": "...", "hour": "...", "dayOfMonth": "...", "month": "...", "dayOfWeek": "..."}, "next_runs": ["2026-08-17T09:00:00", ...]}, or {"error": "..."} for a malformed expression. count is optional (default 5, max 20); next_runs times are in the server's local time zone, starting from now.

🤖 Use this API as a Claude Skill

Want an AI agent (Claude Code, claude.ai, or anything else that supports the Agent Skills format) to use this tool for you on request? Download the skill below and add it:

⬇️ Download SKILL.md · View raw