Vercel Cron Jobs

Vercel cron syntax

Vercel accepts standard five-field expressions with a narrower rule set than Linux:

• No names. MON, SUN, JAN and DEC are rejected. Use numbers.
• One day field at a time. You cannot restrict day of month and day of week together. When one has a value, the other must be *.
• UTC only. To run at 9:00 AM New York time, convert it with the cron timezone converter.

Vercel cron examples

Each expression below passes CronWave's Vercel rules. Load one into the builder to change it.

Plan limits and timing

On Hobby, an expression that would run more than once a day fails the deployment, and a job set for 01:00 can start at any point up to 01:59. If you need precise or frequent runs, the Pro plan is the route Vercel documents.

How the request is sent, and how to secure it

Vercel makes an HTTP GET request to the path on your production deployment. The request carries the user agent vercel-cron/1.0 and an x-vercel-cron-schedule header with the expression that fired, which is useful when several schedules call the same path.

To stop anyone else calling the endpoint, add an environment variable named CRON_SECRET (at least 16 random characters). Vercel then sends it as an Authorization: Bearer header, and your handler compares it.

export function GET(request) {
  const auth = request.headers.get('authorization');
  if (!process.env.CRON_SECRET || auth !== `Bearer ${process.env.CRON_SECRET}`) {
    return new Response('Unauthorized', { status: 401 });
  }
  // do the work
  return Response.json({ ok: true });
}

Reliability: retries, duplicates and redirects

• No retries. Vercel does not retry a failed invocation. Check the logs for errors.
• Best-effort delivery. A run can occasionally be missed or delivered twice, so make the job idempotent.
• Redirects are final. Cron jobs do not follow redirects; a 3xx response ends the invocation.
• Overlap. If a job runs longer than its interval, a second instance can start. Use a lock, shorten the job, or lengthen the interval.
• A missing path. A path that does not exist returns a 404, but Vercel still runs the cron job.

Common Vercel cron mistakes

• Using an hourly schedule on Hobby and wondering why the deployment fails.
• Writing 0 9 * * MON. Use 0 9 * * 1.
• Setting both a day of month and a day of week, for example "the 1st if it is a Monday". Vercel rejects it, and plain cron cannot express it either.
• Expecting local time. Everything is UTC.
• Checking only the schedule when the job does nothing. The expression can be right while the route is protected or redirecting. Test the path directly.

Sources and further reading

• Vercel documentation: Cron Jobs
• Vercel: managing cron jobs, CRON_SECRET and reliability
• Vercel: cron jobs usage and pricing