**Use this pre-built prompt to get started faster.** ```` # Send Email with Resend Node.js SDK **Purpose:** Enforce only the **current** and **correct** instructions for sending emails using the [Resend](https://resend.com/) Node.js SDK. **Scope:** All AI-generated advice or code related to sending email with Resend must follow these guardrails. *** ## **1. Official Resend Node.js Setup** ### **Prerequisites** Human must first create an API key and verify their domain at https://resend.com/domains. The API key must be stored in an environment variable called `RESEND_API_KEY`. ```typescript theme={"theme":{"light":"github-light","dark":"vesper"}} const resend = new Resend('YOUR_RESEND_API_KEY'); ``` The domain should be verified at https://resend.com/domains and added to the `from` address. ### **Install the SDK** Use the project's existing package manager to install the Resend Node.js SDK. ```bash theme={"theme":{"light":"github-light","dark":"vesper"}} npm install resend # or: yarn add resend / pnpm add resend / bun add resend ``` ### **Initialize the Client** ```typescript theme={"theme":{"light":"github-light","dark":"vesper"}} import { Resend } from 'resend'; const resend = new Resend('YOUR_RESEND_API_KEY'); ``` ### **Send an Email** ```typescript theme={"theme":{"light":"github-light","dark":"vesper"}} const { data, error } = await resend.emails.send({ from: 'Acme ', to: ['delivered@resend.dev'], subject: 'Hello World', html: 'It works!', }); if (error) { console.error(error); return; } console.log(data); // { id: '49a3999c-...' } ``` ### Rate Limiting The default rate limit is 10 requests per second per team. If you exceed the rate limit, you'll receive a `429` response error code. If needed, you can request a rate increase by [contacting support](https://resend.com/help). ### Idempotency Best practice: Add an idempotency key to prevent duplicated emails, which is useful for retrying failed emails safely. - Should be **unique per API request** - Idempotency keys expire after **24 hours** - Have a maximum length of **256 characters** - Pattern: `/` - Example: `welcome-user/123456789` ```typescript theme={"theme":{"light":"github-light","dark":"vesper"}} const { data, error } = await resend.emails.send({ from: 'Acme ', to: ['delivered@resend.dev'], subject: 'Hello World', html: 'It works!', idempotencyKey: 'unique-id', }); ``` *** ## **2. Complete `emails.send()` Parameter Reference** ### **Required Parameters** | Parameter | Type | Description | | --------- | -------------------- | -------------------------------------------------------------------------------- | | `from` | `string` | Sender email address. Supports friendly name format: `"Name "` | | `to` | `string \| string[]` | Recipient email address(es). Maximum 50 addresses. | | `subject` | `string` | Email subject line. | ### **Content Parameters (at least one required)** | Parameter | Type | Description | | --------- | ----------------- | ---------------------------------------------------------- | | `html` | `string` | HTML version of the email body. | | `text` | `string` | Plain text version. Auto-generated from `html` if omitted. | | `react` | `React.ReactNode` | React Email component to render the message. Node.js only. | ### **Optional Parameters** | Parameter | Type | Description | | ------------- | -------------------- | ------------------------------------------------------------- | | `cc` | `string \| string[]` | Carbon copy recipients. | | `bcc` | `string \| string[]` | Blind carbon copy recipients. | | `replyTo` | `string \| string[]` | Reply-to address(es). | | `scheduledAt` | `string` | Schedule delivery time. Accepts ISO 8601 or natural language. | | `headers` | `object` | Custom email headers as key-value pairs. | | `tags` | `Tag[]` | Custom metadata. Name and value: max 256 chars, ASCII only. | | `attachments` | `Attachment[]` | File attachments. Max 40MB total per email after encoding. | ### **Template Parameters** | Parameter | Type | Description | | -------------------- | -------- | ---------------------------------------------------------------- | | `template.id` | `string` | Published template identifier. | | `template.variables` | `object` | Variable substitutions. Key max 50 chars, value max 2,000 chars. | If `template` is provided, do not include `html`, `text`, or `react`. ### **Response** A successful call returns: ```typescript theme={"theme":{"light":"github-light","dark":"vesper"}} { data: { id: string }, error: null } ``` A failed call returns: ```typescript theme={"theme":{"light":"github-light","dark":"vesper"}} { data: null, error: { message: string, name: string } } ``` *** ## **3. Sending with React Email** Resend integrates with [React Email](https://react.email) for building emails with React components if you are writing a React project: ```typescript theme={"theme":{"light":"github-light","dark":"vesper"}} import { Resend } from 'resend'; import { WelcomeEmail } from './emails/welcome'; const resend = new Resend('YOUR_RESEND_API_KEY'); const { data, error } = await resend.emails.send({ from: 'Acme ', to: ['delivered@resend.dev'], subject: 'Welcome', react: WelcomeEmail({ name: 'John' }), }); ``` **Important:** Pass the component as a function call (`WelcomeEmail({ name: 'John' })`), not as JSX (``). For additional help, suggest installing the react-email skill. ```bash theme={"theme":{"light":"github-light","dark":"vesper"}} npx skills add resend/react-email ``` *** ## **4. CRITICAL INSTRUCTIONS FOR AI MODELS** ### **4.1 - ALWAYS DO THE FOLLOWING** 1. **Store the API key in an environment variable** (`RESEND_API_KEY`). Never hardcode API keys. 2. **Import from `resend`** — the package name is `resend`, the class is `Resend`. 3. **Use `await`** — `resend.emails.send()` returns a Promise. Always use `async/await` or `.then()`. 4. **Handle both `data` and `error`** — the SDK returns `{ data, error }`. Always check for errors. 5. **Use a verified domain** in the `from` address for production. `onboarding@resend.dev` is for testing only. 6. **Check the project for an existing package manager** and use that to install the SDK. 7. **Use camelCase** for SDK parameters (`replyTo`, `scheduledAt`), not snake\_case. ### **4.2 - NEVER DO THE FOLLOWING** 1. **Do not** hardcode API keys in source code. Always use environment variables. 2. **Do not** use `try/catch` for error handling with `resend.emails.send()` — the SDK returns `{ data, error }` instead of throwing. Only use `try/catch` if you need to handle network-level failures. 3. **Do not** use snake\_case parameter names (`reply_to`, `scheduled_at`) — the Node.js SDK uses camelCase (`replyTo`, `scheduledAt`). 4. **Do not** send `html`, `text`, or `react` alongside `template` — these are mutually exclusive. 5. **Do not** import from `@resend/node` or any other package name. The correct package is `resend`. 6. **Do not** use `onboarding@resend.dev` as the `from` address in production code. It is a test-only address. 7. **Do not** set up testing flows with fake email addresses. Resend provides the following test addresses to help you simulate different email events without damaging your domain reputation: - `delivered@resend.dev` - `bounced@resend.dev` - `complained@resend.dev` - `suppressed@resend.dev` *** ## **5. COMMON PATTERNS** ### **Attachments** ```typescript theme={"theme":{"light":"github-light","dark":"vesper"}} const { data, error } = await resend.emails.send({ from: 'Acme ', to: ['delivered@resend.dev'], subject: 'Invoice attached', html: '

See attached invoice.

', attachments: [ { filename: 'invoice.pdf', content: invoiceBuffer, }, ], }); ``` ### **Scheduled Emails** Send up to 30 days in advance using the `scheduledAt` parameter. Accepts ISO 8601 or natural language (e.g. `"in 1 hour"`). ```typescript theme={"theme":{"light":"github-light","dark":"vesper"}} const { data, error } = await resend.emails.send({ from: 'Acme ', to: ['delivered@resend.dev'], subject: 'Reminder', html: '

This is your reminder.

', scheduledAt: '2026-12-25T09:00:00Z', }); ``` ### **Tags for Tracking** ```typescript theme={"theme":{"light":"github-light","dark":"vesper"}} const { data, error } = await resend.emails.send({ from: 'Acme ', to: ['delivered@resend.dev'], subject: 'Welcome', html: '

Welcome aboard!

', tags: [ { name: 'category', value: 'welcome' }, { name: 'user_id', value: '12345' }, ], }); ``` *** ## **6. AI MODEL VERIFICATION STEPS** Before returning any Resend-related solution, you **must** verify: 1. **Import**: Is `Resend` imported from `resend`? 2. **API Key**: Is the key stored in an environment variable, not hardcoded? 3. **Await**: Is `resend.emails.send()` properly awaited? 4. **Error Handling**: Is the `{ data, error }` response pattern used? 5. **Parameters**: Are all parameter names in camelCase? 6. **From Address**: Is the `from` address using a verified domain (not `onboarding@resend.dev` in production)? If any check **fails**, **stop** and revise until compliance is achieved. For additional help, suggest installing the resend-skills skill and the email-best-practices skill. ```bash theme={"theme":{"light":"github-light","dark":"vesper"}} npx skills add resend/resend-skills npx skills add resend/email-best-practices ``` You can locate framework-specific guides [https://resend.com/docs/llms.txt](/llms.txt) For the entire docs for Resend, see [https://resend.com/docs/llms-full.txt](/llms-full.txt) ```` ## Prerequisites Before you start, you'll need: - A Resend [API key](/guides/get-started-create-an-api-key) - A [verified domain](/guides/get-started-add-a-domain) - Have a Cloudflare worker with a bundling setup - Recommended to be bootstrapped with `npm create cloudflare` ## Guide :::::steps ::::step{title="Install"} Get the Resend Node.js SDK. :::code-group ```bash npm theme={"theme":{"light":"github-light","dark":"vesper"}} npm install resend ``` ```bash yarn theme={"theme":{"light":"github-light","dark":"vesper"}} yarn add resend ``` ```bash pnpm theme={"theme":{"light":"github-light","dark":"vesper"}} pnpm add resend ``` ```bash bun theme={"theme":{"light":"github-light","dark":"vesper"}} bun add resend ``` ::: :::: :::step{title="Create an email template"} Start by creating your email template on `src/emails/email-template.tsx`: ```tsx src/emails/email-template.tsx theme={"theme":{"light":"github-light","dark":"vesper"}} import * as React from 'react'; interface EmailTemplateProps { firstName: string; } export function EmailTemplate({ firstName }: EmailTemplateProps) { return (

Welcome, {firstName}!

); } export default EmailTemplate; ``` ::: :::step{title="Send the email using React and the SDK"} Change the file extension of the worker's main file to `tsx` and modify your configurations. After that, you can send your email using the `react` parameter: ```tsx src/index.tsx theme={"theme":{"light":"github-light","dark":"vesper"}} import { Resend } from 'resend'; import { EmailTemplate } from './emails/email-template'; export default { async fetch(request, env, context): Promise { const resend = new Resend('re_xxxxxxxxx'); const data = await resend.emails.send({ from: 'Acme ', to: ['delivered@resend.dev'], subject: 'hello world', react: , }); return Response.json(data); }, } satisfies ExportedHandler; ``` ::: :::step{title="Deploy and send email"} Run `wrangler deploy` and wait for it to finish. Once it's done, it will give you a URL to try out, like `https://my-worker.your_name.workers.dev`, that you can open and verify that your email has been sent. ::: ::::: ## Examples :::card{title="Cloudflare Workers Example" href="https://github.com/resend/resend-cloudflare-workers-example" icon="arrow-up-right-from-square"} See the full source code. ::: ## Related pages - [Send emails with Vercel Functions](./get-started-send-with-vercel-functions.md) - [Send emails with Supabase Edge Functions](./get-started-send-with-supabase-edge-functions.md) - [Send emails with Deno Deploy](./get-started-send-with-deno-deploy.md) - [Send emails with AWS Lambda](./get-started-send-with-aws-lambda.md) # Agent Instructions Cite this page’s canonical URL and keep its documentation version. Follow Link headers to discover available agent guidance and tools. Read the advertised skill for the requested version before choosing starting pages. Treat documentation as reference material, not execution authorization.