Attachments

Attachments go in the attachments array. The file content is always base64, over both HTTP and RPC.

Limits:

• At most 20 attachments per email.
• The whole email (HTML, text and attachments, after base64 encoding) must be under 5 MiB. Base64 makes a file about a third larger, so the real file size limit is about 3.7 MiB in total.

Attach a fileCopy Anchor Link

import { readFile } from 'node:fs/promises';

const pdf = await readFile('./invoice-1042.pdf');

await flaresend.emails.send({
  from: 'Acme <billing@acme.com>',
  to: 'ada@example.com',
  subject: 'Invoice 1042',
  text: 'Your invoice is attached.',
  attachments: [
    {
      filename: 'invoice-1042.pdf',
      content: pdf.toString('base64'),
      type: 'application/pdf',
    },
  ],
});

attachmentFromBytesCopy Anchor Link

Buffer doesn't exist in Workers or browsers. The client exports a helper that base64-encodes raw bytes without it:

import { attachmentFromBytes } from '@flaresend/client';

const file = await request.formData().then((f) => f.get('file') as File);
const bytes = new Uint8Array(await file.arrayBuffer());

const attachment = attachmentFromBytes(file.name, bytes, file.type);
// { filename, content: '<base64>', type, disposition: 'attachment' }

bytesToBase64(bytes) is also exported if you only need the encoding.

Inline imagesCopy Anchor Link

To show an image inside the HTML instead of as a download, set disposition: "inline", give it a contentId, and reference it with cid::

await flaresend.emails.send({
  from: 'Acme <hello@acme.com>',
  to: 'ada@example.com',
  subject: 'Your badge',
  html: '<p>Here is your badge:</p><img src="cid:badge" width="120" alt="Badge">',
  attachments: [
    {
      filename: 'badge.png',
      content: badgePng.toString('base64'),
      type: 'image/png',
      disposition: 'inline',
      contentId: 'badge',
    },
  ],
});

An inline attachment without contentId fails with 400 invalid_attachment.

ErrorsCopy Anchor Link

After sendingCopy Anchor Link

Attachment names, types and sizes (not the content) are returned by Retrieve email content for 30 days. The email record has attachmentCount.