There are two ways to send attachments:
  1. From a remote file
  2. From a local file
We currently do not support sending attachments when using our batch endpoint.

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Send attachments from a remote file

Include the path parameter to send attachments from a remote file. This parameter accepts a URL to the file you want to attach. Define the file name that will be attached using the filename parameter. 
import { Resend } from 'resend';

const resend = new Resend('re_xxxxxxxxx');

await resend.emails.send({
  from: 'Acme <onboarding@resend.dev>',
  to: ['delivered@resend.dev'],
  subject: 'Receipt for your payment',
  html: '<p>Thanks for the payment</p>',
  attachments: [
    {
      path: 'https://resend.com/static/sample/invoice.pdf',
      filename: 'invoice.pdf',
    },
  ],
});

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Send attachments from a local file

Include the content parameter to send attachments from a local file. This parameter accepts the Base64 encoded content of the file you want to attach. Define the file name that will be attached using the filename parameter. 
import { Resend } from 'resend';
import fs from 'fs';

const resend = new Resend('re_xxxxxxxxx');

const filepath = `${__dirname}/static/invoice.pdf`;
const attachment = fs.readFileSync(filepath).toString('base64');

await resend.emails.send({
  from: 'Acme <onboarding@resend.dev>',
  to: ['delivered@resend.dev'],
  subject: 'Receipt for your payment',
  text: '<p>Thanks for the payment</p>',
  attachments: [
    {
      content: attachment,
      filename: 'invoice.pdf',
    },
  ],
});

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Embed Images using CID

You can optionally embed an image in the HTML body of the email. Both remote and local attachments are supported. All attachment requirements, options, and limitations apply to embedded inline images as well. Embedding images requires two steps: 1. Add the CID in the email HTML. Use the prefix cid: to reference the ID in the src attribute of an image tag in the HTML body of the email. 
<img src="cid:logo-image" />
2. Reference the CID in the attachment Include the content_id parameter in the attachment object (e.g. content_id: "logo-image"). The ID is an arbitrary string set by you, and must be less than 128 characters. Learn more about embedding images.

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Attachment Limitations

  • Emails can be no larger than 40MB (including attachments after Base64 encoding).
  • Not all file types are supported. See the list of unsupported file types.
  • Emails with attachments cannot be scheduled.
  • Emails with attachments cannot be sent using our batching endpoint.
All attachments (including inline images) do not currently display in the emails dashboard when previewing an email’s HTML.

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Examples

Attachments with Next.js (remote file)

See the full source code.

Attachments with Next.js (local file)

See the full source code.