MJML is a markup language and framework that lets developers build responsive email layouts using a simplified component-like syntax. Instead of writing complex table HTML manually, you write MJML tags and compile them into email-compatible HTML. MJML is popular with engineering teams because it provides higher-level abstractions while still producing output that works across many email clients.
Why Teams Use MJML
Email HTML is constrained, and hand-coding layouts can be slow and error-prone. MJML speeds up development by providing reusable components like sections, columns, and buttons. It is most effective when paired with MJML compilation because the compilation step turns abstractions into client-compatible HTML, including inlining styles and generating the table structures needed for compatibility.
How MJML Relates to Classic Email Layout Patterns
Even though MJML feels modern, its output is typically based on proven email patterns. Many layouts still depend on table based layout under the hood because that is what works reliably across strict clients. Understanding this relationship helps when debugging. If a layout breaks in Outlook, you often need to inspect the compiled HTML rather than assuming the MJML source is the problem.
Practical Constraints to Keep in Mind
If you maintain custom MJML components, treat them like a library. Version them, test them against key clients, and document breaking changes. Custom components can introduce subtle markup differences that only show up after compilation.
MJML-generated HTML can become large, especially when templates include many modules and inline styles. That can increase the risk of hitting an email size limit and getting clipped in clients like Gmail. Keep templates lean, avoid unused components, and reuse blocks consistently. Also validate the compiled output, because MJML abstraction does not eliminate the need for real client testing.
MJML and Topol
Topol supports developer-friendly email building workflows by producing predictable output and structured editing patterns that can complement MJML-based processes or replace manual HTML assembly. Learn more at Topol or create an account at Topol signup.