MJML
An MIT-licensed email framework that compiles component markup into responsive email HTML.
About MJML
MJML is an open-source email framework released under the MIT license. It lets developers write email layouts in a markup language made of components, then compiles that markup into responsive email HTML. The output uses nested tables and inline CSS, which are the techniques most email clients require. MJML was created in early 2015 by developers at Mailjet, who built it while working on a drag-and-drop email builder. The framework's engine is built in React.js. The homepage describes the output as responsive on most popular email clients, including Outlook. It does not list which clients are covered beyond that wording.
Key features
- Compiles component markup into responsive email HTML with nested tables and inline CSS
- Semantic section and column tags such as mj-section and mj-column
- Built-in components ranging from mj-image to higher-level mj-article
- Custom components that users can build and reuse across emails
- Responsive layout on most popular email clients, including Outlook
- Engine built in React.js, designed for reusing and extending components
Best for: Developers and teams who hand-code email templates and want responsive output without writing table-based layouts and client-specific CSS.
Good for
- Free and open source under the MIT license
- Semantic syntax reduces the need for nested HTML tables and client-specific CSS
- Reusable components let users focus on content rather than styling
Watch out for
- Responsive output is described for most popular email clients, not all of them
MJML at a glance
- Website
- mjml.io
- Category
- Productivity › Email Tools
- Type
- Online tool
- Pricing
- Free
- Open source
- Yes
- Last checked
- Oct 9, 2026 · Online when checked
- Listed
- Oct 9, 2026
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MJML FAQ
Is MJML free to use?
Yes. MJML is listed as free and is released as open-source software under the MIT license.
Does MJML output work in Outlook?
The homepage states that MJML is responsive by design on most popular email clients, even Outlook.
Can I create my own components?
Yes. Besides the components included with MJML, users can build their own reusable components.
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