mjml

name	mjml
description	Build responsive HTML emails using MJML (Mailjet) — semantic XML tags, very low friction, excellent client compatibility. Use when the user has chosen MJML, wants quick templates, or needs something a non-developer can edit.

MJML Workflow

MJML (https://github.com/mjmlio/mjml) is Mailjet's open-source email framework. Semantic XML-like tags compile to robust, cross-client HTML. Lowest friction of the three frameworks and the easiest for non-developers.

Setup

Global CLI (fastest for one-offs):

npm install -g mjml
mjml -h

Or per-project:

npm init -y
npm install mjml

For live editing, use the online editor at https://mjml.io/try-it-live or VSCode extension attilabuti.vscode-mjml.

Minimal template (email.mjml)

<mjml>
  <mj-head>
    <mj-title>Your subject line</mj-title>
    <mj-preview>Preview text — 80-90 chars</mj-preview>
    <mj-attributes>
      <mj-all font-family="Helvetica, Arial, sans-serif" />
      <mj-text font-size="16px" line-height="1.5" color="#333333" />
      <mj-button background-color="#2c3e50" color="#ffffff" border-radius="4px" />
    </mj-attributes>
    <mj-style>
      .footer-link { color: #888888; text-decoration: underline; }
    </mj-style>
  </mj-head>

  <mj-body background-color="#f3f3f3" width="600px">
    <mj-section background-color="#ffffff" padding="24px">
      <mj-column>
        <mj-image src="https://example.com/logo.png" alt="Company" width="140px" />
      </mj-column>
    </mj-section>

    <mj-section background-color="#ffffff" padding="0 24px 24px">
      <mj-column>
        <mj-text font-size="24px" font-weight="bold">Headline</mj-text>
        <mj-text>Body copy.</mj-text>
        <mj-button href="https://example.com">Call to action</mj-button>
      </mj-column>
    </mj-section>

    <mj-section padding="16px">
      <mj-column>
        <mj-text align="center" font-size="12px" color="#888888">
          <a href="https://example.com/unsubscribe" class="footer-link">Unsubscribe</a>
        </mj-text>
      </mj-column>
    </mj-section>
  </mj-body>
</mjml>

Core tags

Tag	Purpose
<mjml>	Root
<mj-head>	Metadata: title, preview, global attributes, custom CSS
<mj-title>	Subject line (used in preview / by some clients)
<mj-preview>	Preheader text
<mj-attributes>	Set defaults for all instances of a tag
<mj-style>	Custom CSS (inlined into output)
<mj-body>	Email body wrapper
<mj-section>	Full-width horizontal band
<mj-group>	Keeps columns side-by-side on mobile
<mj-column>	Vertical container inside a section
<mj-text>	Paragraph/heading text
<mj-image>	Responsive image
<mj-button>	Bulletproof button (VML fallback automatic)
<mj-divider>	Horizontal rule
<mj-spacer>	Vertical space
<mj-social> + <mj-social-element>	Social icon row
<mj-navbar> + <mj-navbar-link>	Horizontal nav
<mj-hero>	Full-width image banner with overlay content
<mj-carousel>	Image carousel (limited client support)
<mj-raw>	Inject raw HTML (e.g., VML, conditionals) — escape hatch

Build

mjml email.mjml -o email.html                 # single file
mjml email.mjml -o email.html --config.minify=true
mjml templates/*.mjml -o build/               # directory
mjml email.mjml --config.validationLevel=strict

Via Node API:

import mjml2html from 'mjml';
const { html, errors } = mjml2html(mjmlSource, { minify: true, validationLevel: 'strict' });

Templating with includes

<mj-include path="./header.mjml" />

For variable substitution, combine MJML with a templating engine (Handlebars, Liquid, Nunjucks) before passing to mjml2html — MJML itself has no variable interpolation.

Example pipeline:

import Handlebars from 'handlebars';
import mjml2html from 'mjml';
import fs from 'fs';

const template = Handlebars.compile(fs.readFileSync('email.mjml', 'utf8'));
const rendered = template({ firstName: 'Daniel', cta: 'https://...' });
const { html } = mjml2html(rendered);
fs.writeFileSync('email.html', html);

Theming via <mj-attributes>

Set once in <mj-head>, apply everywhere:

<mj-attributes>
  <mj-all font-family="Inter, Helvetica, sans-serif" />
  <mj-text color="#1a1a1a" line-height="1.6" />
  <mj-button background-color="#2c3e50" color="#ffffff" border-radius="6px" padding="12px 24px" />
  <mj-class name="muted" color="#888888" font-size="14px" />
</mj-attributes>

Use the named class: <mj-text mj-class="muted">Fine print</mj-text>.

Known pitfalls

• <mj-column> stacks on mobile by default. Use <mj-group> to keep them side-by-side.
• Percentages on column widths must sum to 100% per section.
• Custom CSS in <mj-style> is inlined by default — use inline="inline" explicitly for clarity, or <mj-style> without it for head-only CSS (survives for media queries).
• Hero images: use <mj-hero> for background-image banners — handles VML fallback automatically.
• Validation errors hidden: always run with --config.validationLevel=strict during dev.

Hand off to email-client-gotchas (always) and inline-and-test for preview/send workflow.