> ## Documentation Index
> Fetch the complete documentation index at: https://docs.lettr.com/llms.txt
> Use this file to discover all available pages before exploring further.
# Cloudflare Workers
> Send transactional emails from Cloudflare Workers using Lettr's HTTP API, running on the global edge network with instant cold starts.
Send transactional emails from Cloudflare Workers using Lettr's HTTP API. Workers run on Cloudflare's global edge network with instant cold starts and zero-millisecond latency — perfect for email APIs that need to be fast anywhere in the world.
Using Cursor? [Jump straight in using this prompt](https://cursor.com/link/prompt?text=Help%20me%20add%20a%20Lettr%20sending%20example%20for%20Cloudflare%20Workers%2C%20or%20migrate%20my%20current%20Worker%20email%20sending%20solution%20to%20Lettr%20using%20these%20docs%3A%20https%3A%2F%2Fdocs.lettr.com%2Fquickstart%2Fserverless%2Fcloudflare-quickstart)
## Prerequisites
Before you begin, make sure you have:
Create an API key in the Lettr dashboard
Add and verify your sending domain
You'll also need:
* **Cloudflare account** (free tier works)
* **Wrangler CLI** installed (`npm install -g wrangler`)
* **Node.js 18.x or 20.x** for local development
## Quick Setup
```bash theme={null}
npm create cloudflare@latest my-email-worker
cd my-email-worker
```
When prompted, choose:
* Type: "Hello World" Worker
* TypeScript: Yes (recommended)
* Git: Yes (optional)
* Deploy: No (we'll deploy later)
```bash theme={null}
npm install lettr
```
The SDK works seamlessly with Workers and provides a clean, type-safe interface.
```bash theme={null}
npx wrangler secret put LETTR_API_KEY
```
When prompted, paste your Lettr API key (starts with `lttr_`).
Secrets are encrypted environment variables that are not visible in your code or Wrangler config. They're perfect for API keys.
```bash theme={null}
npm run deploy
```
Your Worker will be deployed to Cloudflare's edge network and available at `https://my-email-worker.your-subdomain.workers.dev`.
## Worker Implementation
Create or update `src/index.ts`:
```typescript theme={null}
import { Lettr } from 'lettr';
export interface Env {
LETTR_API_KEY: string;
FROM_EMAIL?: string;
}
export default {
async fetch(request: Request, env: Env): Promise {
// Only allow POST requests
if (request.method !== 'POST') {
return new Response('Method not allowed', { status: 405 });
}
// Initialize Lettr client
const lettr = new Lettr(env.LETTR_API_KEY);
try {
const body = await request.json() as {
to: string | string[];
subject: string;
html?: string;
text?: string;
};
const { to, subject, html, text } = body;
// Validate required fields
if (!to || !subject || (!html && !text)) {
return Response.json(
{ error: 'Missing required fields: to, subject, and html or text' },
{ status: 400 }
);
}
// Send email
const result = await lettr.emails.send({
from: env.FROM_EMAIL || 'noreply@yourdomain.com',
to: Array.isArray(to) ? to : [to],
subject,
html,
text,
});
console.log(`Email sent successfully. Request ID: ${result.request_id}`);
return Response.json({
success: true,
requestId: result.request_id,
accepted: result.accepted,
});
} catch (error: any) {
console.error('Failed to send email:', error);
return Response.json(
{ error: error.message || 'Failed to send email' },
{ status: error.status || 500 }
);
}
},
};
```
Cloudflare Workers use the `Env` interface to define environment variables and secrets. The Lettr SDK automatically handles retries and provides detailed error messages.
## Configuration
Configure your Worker in `wrangler.toml`:
```toml theme={null}
name = "my-email-worker"
main = "src/index.ts"
compatibility_date = "2024-01-01"
# Non-sensitive environment variables
[vars]
FROM_EMAIL = "noreply@yourdomain.com"
# Secrets (set via wrangler secret put)
# LETTR_API_KEY = "set via CLI"
```
Never commit API keys to `wrangler.toml`. Always use `wrangler secret put` for sensitive values.
## What's Next
Learn about deployment, monitoring, and advanced patterns
Deploy on AWS Lambda
Deploy on Vercel
Complete API documentation