Automatically opens your browser to preview Node.js email messages sent with Nodemailer. Made for Lad!

Usage no npm install needed!

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



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Automatically opens your browser to preview Node.js email messages sent with Nodemailer. Made for Lad!

Table of Contents


demo screenshot



npm install preview-email


yarn add preview-email


NOTE: You should probably just use email-templates directly instead of using this package.

The function previewEmail returns a Promise which resolves with a URL. We automatically open the browser to this URL unless you specify as false (see Options for more info).

const previewEmail = require('preview-email');
const nodemailer = require('nodemailer');

const transport = nodemailer.createTransport({
  jsonTransport: true

// <>
const message = {
  from: '',
  to: '',
  subject: 'Hello world',
  html: '<p>Hello world</p>',
  text: 'Hello world',
  attachments: [ { filename: 'hello-world.txt', content: 'Hello world' } ]

// note that `attachments` will not be parsed unless you use
// `previewEmail` with the results of `transport.sendMail`
// e.g. `previewEmail(JSON.parse(res.message));` where `res`
// is `const res = await transport.sendMail(message);`


Custom Preview Template and Stylesheets

Using the options.template object, you can define your own template for rendering (e.g. get inspiration from template.pug and write your own!):

const path = require('path');

// ...

previewEmail(message, { template: path.join(__dirname, 'my-custom-preview-template.pug') })


Thanks to the debug package, you can easily debug output from preview-email:

DEBUG=preview-email node app.js


  • message (Object) - a Nodemailer message configuration object
  • options (Object) - an object with the following two properties:
    • id (String) - a unique ID for the file name created for the preview in dir (defaults to uuid.v4() from uuid)
    • dir (String) - a path to a directory for saving the generated email previews (defaults to os.tmpdir(), see os docs for more insight)
    • open (Object or Boolean) - an options object that is passed to open (defaults to { wait: false }) - if set to false then it will not open the email automatically in the browser using open, and if set to true then it will default to { wait: false }
    • template (String) - a file path to a pug template file (defaults to preview-email's template.pug by default) - this is where you can pass a custom template for rendering email previews, e.g. your own stylesheet
    • urlTransform (Function (path) => url) - a function to build preview url from file path (defaults to (path) => 'file://[file path]') - this is where you can customize the opened path to handle WSL to Windows transformation or build a http url if dir is served.


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Nick Baugh


MIT © Nick Baugh