MJML

MJML is an open-source responsive email framework that makes designing responsive emails easy by abstracting the complex, fragile HTML and inline CSS required for cross-client compatibility into a concise semantic markup language. Originally developed and maintained by Mailjet, the framework solves the notoriously difficult problem of rendering HTML emails consistently across the dozens of email clients in active use, including Outlook, Gmail, Apple Mail, Yahoo, and mobile clients, without requiring developers to write table-based layouts or conditional Outlook-specific CSS hacks. The component-based architecture provides semantic tags for common email building blocks including mj-section, mj-column, mj-text, mj-image, mj-button, mj-social, mj-navbar, mj-carousel, mj-accordion, and mj-table, which compile to responsive HTML with appropriate media queries, MSO conditional comments for Outlook, and vendor-prefixed CSS. The framework handles fluid responsive behavior automatically, with sections stacking vertically on mobile and expanding horizontally on desktop. Templates are available for newsletters, transactional emails, and promotional campaigns. The MJML ecosystem includes a desktop application for visual editing, a live online playground, CLI tools for batch processing, and integrations with GrapesJS, Parcel.io, Spatie, Typeform, and Email Love. The framework powers email rendering at companies including Typeform and organizations using Litmus for email testing. Available via npm, Homebrew, and CDN, with plugins for React, Vue, and server-side rendering through Node.js APIs. Copyright 2026 Mailjet SAS.