Cloudflare Cron Triggers

Schedule Workers execution using cron expressions. Runs on Cloudflare's global network during underutilized periods.

Key Features

UTC-only execution - All schedules run on UTC time
5-field cron syntax - Quartz scheduler extensions (L, W, #)
Global propagation - 15min deployment delay
At-least-once delivery - Rare duplicate executions possible
Workflow integration - Trigger long-running multi-step tasks
Green Compute - Optional carbon-aware scheduling during low-carbon periods

Cron Syntax

 ┌─────────── minute (0-59)
 │ ┌───────── hour (0-23)
 │ │ ┌─────── day of month (1-31)
 │ │ │ ┌───── month (1-12, JAN-DEC)
 │ │ │ │ ┌─── day of week (1-7, SUN-SAT, 1=Sunday)
 * * * * *

Special chars: * (any), , (list), - (range), / (step), L (last), W (weekday), # (nth)

Common Schedules

*/5 * * * *        # Every 5 minutes
0 * * * *          # Hourly
0 2 * * *          # Daily 2am UTC (off-peak)
0 9 * * MON-FRI    # Weekdays 9am UTC
0 0 1 * *          # Monthly 1st midnight UTC
0 9 L * *          # Last day of month 9am UTC
0 10 * * MON#2     # 2nd Monday 10am UTC
*/10 9-17 * * MON-FRI  # Every 10min, 9am-5pm weekdays

Quick Start

wrangler.jsonc:

{
  "name": "my-cron-worker",
  "triggers": {
    "crons": ["*/5 * * * *", "0 2 * * *"]
  }
}

Handler:

export default {
  async scheduled(
    controller: ScheduledController,
    env: Env,
    ctx: ExecutionContext,
  ): Promise<void> {
    console.log("Cron:", controller.cron);
    console.log("Time:", new Date(controller.scheduledTime));
    
    ctx.waitUntil(asyncTask(env)); // Non-blocking
  },
};

Test locally:

npx wrangler dev
curl "http://localhost:8787/__scheduled?cron=*/5+*+*+*+*"

Limits

Free: 3 triggers/worker, 10ms CPU
Paid: Unlimited triggers, 50ms CPU
Propagation: 15min global deployment
Timezone: UTC only

Reading Order

New to cron triggers? Start here:

This README - Overview and quick start
configuration.md - Set up your first cron trigger
api.md - Understand the handler API
patterns.md - Common use cases and examples

Troubleshooting? Jump to gotchas.md

In This Reference

configuration.md - wrangler config, env-specific schedules, Green Compute
api.md - ScheduledController, noRetry(), waitUntil, testing patterns
patterns.md - Use cases, monitoring, queue integration, Durable Objects
gotchas.md - Timezone issues, idempotency, security, testing

README.md