1# Cloudflare Cron Triggers
2 
3Schedule Workers execution using cron expressions. Runs on Cloudflare's global network during underutilized periods.
4 
5## Key Features
6 
7- **UTC-only execution** - All schedules run on UTC time
8- **5-field cron syntax** - Quartz scheduler extensions (L, W, #)
9- **Global propagation** - 15min deployment delay
10- **At-least-once delivery** - Rare duplicate executions possible
11- **Workflow integration** - Trigger long-running multi-step tasks
12- **Green Compute** - Optional carbon-aware scheduling during low-carbon periods
13 
14## Cron Syntax
15 
16```
17 ┌─────────── minute (0-59)
18 │ ┌───────── hour (0-23)
19 │ │ ┌─────── day of month (1-31)
20 │ │ │ ┌───── month (1-12, JAN-DEC)
21 │ │ │ │ ┌─── day of week (1-7, SUN-SAT, 1=Sunday)
22 * * * * *
23```
24 
25**Special chars:** `*` (any), `,` (list), `-` (range), `/` (step), `L` (last), `W` (weekday), `#` (nth)
26 
27## Common Schedules
28 
29```bash
30*/5 * * * *        # Every 5 minutes
310 * * * *          # Hourly
320 2 * * *          # Daily 2am UTC (off-peak)
330 9 * * MON-FRI    # Weekdays 9am UTC
340 0 1 * *          # Monthly 1st midnight UTC
350 9 L * *          # Last day of month 9am UTC
360 10 * * MON#2     # 2nd Monday 10am UTC
37*/10 9-17 * * MON-FRI  # Every 10min, 9am-5pm weekdays
38```
39 
40## Quick Start
41 
42**wrangler.jsonc:**
43```jsonc
44{
45  "name": "my-cron-worker",
46  "triggers": {
47    "crons": ["*/5 * * * *", "0 2 * * *"]
48  }
49}
50```
51 
52**Handler:**
53```typescript
54export default {
55  async scheduled(
56    controller: ScheduledController,
57    env: Env,
58    ctx: ExecutionContext,
59  ): Promise<void> {
60    console.log("Cron:", controller.cron);
61    console.log("Time:", new Date(controller.scheduledTime));
62    
63    ctx.waitUntil(asyncTask(env)); // Non-blocking
64  },
65};
66```
67 
68**Test locally:**
69```bash
70npx wrangler dev
71curl "http://localhost:8787/__scheduled?cron=*/5+*+*+*+*"
72```
73 
74## Limits
75 
76- **Free:** 3 triggers/worker, 10ms CPU
77- **Paid:** Unlimited triggers, 30s CPU (<1hr interval) / 15min CPU (≥1hr interval)
78- **Propagation:** 15min global deployment
79- **Timezone:** UTC only
80 
81## Reading Order
82 
83**New to cron triggers?** Start here:
841. This README - Overview and quick start
852. [configuration.md](./configuration.md) - Set up your first cron trigger
863. [api.md](./api.md) - Understand the handler API
874. [patterns.md](./patterns.md) - Common use cases and examples
88 
89**Troubleshooting?** Jump to [gotchas.md](./gotchas.md)
90 
91## In This Reference
92- [configuration.md](./configuration.md) - wrangler config, env-specific schedules, Green Compute
93- [api.md](./api.md) - ScheduledController, noRetry(), waitUntil, testing patterns
94- [patterns.md](./patterns.md) - Use cases, monitoring, queue integration, Durable Objects
95- [gotchas.md](./gotchas.md) - Timezone issues, idempotency, security, testing
96 
97## See Also
98- [workflows](../workflows/) - Alternative for long-running scheduled tasks
99- [workers](../workers/) - Worker runtime documentation
100