mjml-cli

Installation

We recommend installing and using MJML locally, in a project folder where you'll use MJML:

bash

npm install mjml

In the folder where you installed MJML you can now run:

bash

./node_modules/.bin/mjml input.mjml

To avoid typing ./node_modules/.bin/, add it to your PATH:

bash

export PATH="$PATH:./node_modules/.bin"

You can now run MJML directly, in that folder:

bash

mjml input.mjml

MJML is written with NodeJS You can download and install the MJML engine from NPM.

Command Line Interface

In addition to the translation engine, which converts MJML to email HTML, we've bundled a Command Line Interface (CLI) helping you to achieve the basic features it offers and integrate it seamlessly in your development flow.

Render MJML to HTML

bash

mjml input.mjml

It will output a HTML file called input.html. Input can also be a directory.

Migrate MJML3 to MJML4

bash

$> mjml -m input.mjml -o result.mjml

It will output a MJML file called result.mjml.

Validate MJML

bash

$> mjml -v input.mjml

It will log validation errors. If there are errors, exits with code 1. Otherwise, exits with code 0.

Render and redirect the result to stdout

bash

mjml -s input.mjml

# or

mjml --stdout input.mjml

Render and redirect the result to a file

bash

mjml input.mjml -o my-email.html

# or

mjml input.mjml --output my-email.html

You can output the resulting email responsive HTML in a file. If the output file does not exist it will be created, but output directories must already exist. If output is a directory, output file(s) will be output/input-file-name.html

Set the validation mode

bash

mjml -l skip -r input.mjml

Accepted values are

'normal' : (default) will display validation messages but compile anyway
'skip' : the file is rendered without being validated
'strict' : will throw an error if validation fails

Watch changes on a file

bash

mjml -w input.mjml

# or

mjml --watch input.mjml

If you like live-coding, you might want to use the -w option that enables you to re-render your file every time you save it. It can be time-saving when you can just split you screen and see the HTML output modified when you modify your MJML.

Of course, the -w option can be used with an --output option too.

Available options

bash

mjml input.mjml --config.optionName value

# or

mjml input.mjml -c.optionName value

All the options that can be passed to mjml2html (see general documentation) can be provided. The most common ones are detailed below.

Minify and beautify the output HTML

bash

$> mjml input.mjml --config.beautify true --config.minify false

These are the default options.

Change minify options

bash

$> mjml input.mjml --config.minifyOptions='{"minifyCss": true, "removeEmptyAttributes": false}'

Defaults when minify is enabled (htmlnano):

collapseWhitespace: true
minifyCss: 'lite' (if not provided)
removeEmptyAttributes: true
removeComments: 'safe'
minifyJs: false

See htmlnano documentation for more options, and cssnano for minifyCss presets/options.

Compatibility note:

The CSS minifier is configured via minifyCss. For backward compatibility, minifyCSS is still accepted and mapped internally:
- {"minifyCSS": false} → disables CSS minification
- {"minifyCSS": true} → enables CSS minification with the 'lite' preset
To customize string quotation, pass a cssnano option, for example:
- --config.minifyOptions '{"minifyCss":{"preset":["default", {"normalizeString":{"preferredQuote":"single"}}]}}'

Sanitize template variables in CSS

When your MJML contains template variables inside <mj-style> or inline style="...", enable sanitization so CSS minification (PostCSS/cssnano) doesn't parse your template tokens:

bash

$> mjml input.mjml --config.sanitizeStyles true --config.minify true

Alternatively, keep HTML minification but skip CSS minification entirely:

bash

$> mjml input.mjml --config.minify true --config.minifyOptions='{"minifyCss": false}'

Allow mixed template syntaxes

By default, mixing block tokens and CSS tokens in the same document is disallowed to avoid subtle parsing issues. Opt in with:

bash

$> mjml input.mjml --config.sanitizeStyles true --config.minify true --config.allowMixedSyntax true

Specify template syntax delimiters

You can provide one or more template syntaxes via JSON. Each entry is an object with prefix and suffix:

bash

$> mjml input.mjml \
	--config.sanitizeStyles true \
	--config.templateSyntax='[{"prefix":"[[","suffix":"]]"},{"prefix":"{{","suffix":"}}"}]'

This is equivalent to setting the same templateSyntax array in .mjmlconfig.js or passing it programmatically.

Change juice options (library used for inlining mj-style css)

bash

$> mjml input.mjml --config.juiceOptions='{"preserveImportant": true}'

The defaults are "applyStyleTags": false, "insertPreservedExtraCss": false, "removeStyleTags": false
See juice documentation for more available options

Preserve specific tags when using inline mj-style

bash

$> mjml input.mjml --config.juicePreserveTags='{"myTag": { "start": "<#", "end": "</#" }}'

When using <mj-style inline="inline"> the css will be inlined using the juice library. As a side effect, juice will convert all tags' attributes into lower case. If you need to preserve some cases (i.e. for a templating lib) you can specify the tags to preserve. With the example above, all tags of the form <# myVar="" > or </# myVar="" > will be left untouched. By default juice already ignores <% EJS %> and {{ HBS }} tags.

Override base path for mj-include relative paths

bash

$> mjml ./my-project/input.mjml --config.filePath ./my-partials/

If you like to keep your partials together and you want to be able to mj-include them without having to change the relative path of the includes depending on the compiled file path, you can use this option. In this exemple, <mj-include path="./header.mjml" /> will include ./my-partials/header.mjml, ignoring the actual path of input.mjml.

Allow includes (opt-in)

By default, includes are ignored for security (ignoreIncludes: true). Enable them during local development with --config.allowIncludes true:

bash

$> mjml input.mjml --config.allowIncludes true

When enabled, include paths are restricted to the directory of the input file and its subdirectories. Absolute paths and paths escaping the project directory are denied.

Allowlist include directories

If your includes live outside the template folder (e.g., a sibling _common directory), you can explicitly allow additional roots with includePath. Paths are resolved relative to --config.filePath when provided.

bash

# Allow includes and declare two additional roots (JSON array)
$> mjml template.mjml \
	--config.filePath /project/templates/newsletter \
	--config.allowIncludes true \
	--config.includePath '["../_common","../vendor"]'

# Or provide absolute paths
$> mjml template.mjml \
	--config.filePath /project/templates/newsletter \
	--config.allowIncludes true \
	--config.includePath '["/project/templates/_common","/project/vendor"]'

Notes:

includePath accepts a string or a JSON array of paths.
Allowed roots are the filePath directory plus any includePath entries; absolute paths outside these roots and parent-directory escapes remain denied.
Relative includePath entries are resolved against filePath (or the template file’s directory when filePath isn’t set).

Security notes:

Includes are ignored by default (ignoreIncludes: true). Enable explicitly only when needed.
Paths are fully URL-decoded before validation (handles double/triple encoding).
Early rejects: absolute paths, UNC paths (//server/... or \\server\\...), Windows drive letters (C:\...), and null bytes (%00).
Canonical checks: we resolve and follow symlinks with realpath and verify the target stays inside filePath or includePath roots.
Allowed file types: mjml, css, and html via <mj-include type="...">; other extensions are not supported.

Best practices for shared partials

If templates reference partials relative to a shared base (e.g., ./_common/header.mjml), set --config.filePath to that base.
If templates use relative paths to siblings (e.g., ../_common/header.mjml), keep paths as-is and use --config.includePath to allowlist the sibling directories.
Always run with --config.allowIncludes true when developing locally; production defaults should keep includes ignored unless explicitly needed.

Log error stack

bash

$> mjml input.mjml --config.stack true