Nodemailer plugin that will inline base64 images

Usage no npm install needed!

<script type="module">
  import nodemailerPluginInlineBase64 from '';


Nodemailer plugin for handling inline Base64 images as attachments

This plugin will convert base64-encoded images in your nodemailer email to be inline ("CID-referenced") attachments within the email. Inline attachments are useful because them embed the image inside the actual email, so it's viewable even if the user is checking their email without an internet connection. But if you're OK with requiring that the user be online to see the image, then consider hosting your images from AWS Cloudfront using nodemailer-base64-to-s3.

Base64 images are generally a bad idea because they aren't supported in most email clients. This Nodemailer plugin will take base64 images in your email html in the form:

<img src="data:image/*;base64,...">

and replace it with a CID-referenced attachment that works in all email clients.


yarn add nodemailer-plugin-inline-base64


npm install nodemailer-plugin-inline-base64 --save


1. Load the nodemailer-plugin-inline-base64 plugin:

var inlineBase64 = require('nodemailer-plugin-inline-base64');

2. Attach it as a 'compile' handler for a nodemailer transport object

nodemailerTransport.use('compile', inlineBase64(options))

Options allow to set CID prefix1 {cidPrefix: 'somePrefix_'}, then all inline images will have prefix in cid, i.e.: cid:somePrefix_5fe3b631c651bdb1. If you don't need this, you can use inlineBase64 plugin without options.


var nodemailer = require('nodemailer');
var inlineBase64 = require('nodemailer-plugin-inline-base64');
transporter.use('compile', inlineBase64({cidPrefix: 'somePrefix_'}));
    from: '',
    to: '',
    html: '&lt;img src="data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAlgAAAACCAYAAACE7KJkAAAAI0lEQVRYR+3DMQ0AAAgDsKlFzZxgEhOcbdIEAIBf7Y6qqn8P0MMQZPno7TMAAAAASUVORK5CYII=">'


1 It might be useful for reply email processing, example with MailParser

mp.on("attachment", function(attachment, mail){
    if (!attachment.contentId.includes('somePrefix')) { // process only images attached by user in reply
        // ...