Paste your MJML above. MailViewr compiles it to responsive, Outlook-safe HTML right in your browser using the official MJML engine — preview across email clients, then download the generated HTML for any ESP. Free, no signup, no install.
The full conversion workflow — from MJML source to verified, downloadable HTML — in one place.
Paste your MJML source into the editor. MailViewr auto-detects the <mjml> root and switches to MJML mode automatically.
Click Preview and MailViewr compiles your MJML to responsive, Outlook-safe HTML using the official MJML engine — no install or signup.
See the compiled HTML render across Gmail, Outlook, Apple Mail and mobile — including dark mode — before you download.
Click </> button to view and download the compiled, email-ready HTML file. Paste it into any ESP — Mailchimp, SendGrid, Klaviyo and more.
Paste MJML like this into the editor above — MailViewr compiles it and gives you clean HTML to download.
<mjml>
<mj-body>
<mj-section>
<mj-column>
<mj-text font-size="20px">Welcome aboard 🎉</mj-text>
<mj-button href="https://example.com">Get started</mj-button>
</mj-column>
</mj-section>
</mj-body>
</mjml>Responsive, Outlook-safe HTML
→ downloadable as a .html file
→ paste into any ESP
→ previewed across Gmail,
Outlook & Apple Mail firstMJML compiles to HTML, so you write far less code and get responsive, Outlook-safe output automatically. MailViewr handles the conversion in the browser — no Node, no CLI.
| Aspect | MJML | Hand-written HTML |
|---|---|---|
| Responsiveness | Automatic, mobile-first | Manual media queries |
| Outlook support | Generated table markup, Word-safe | You write the VML/conditionals |
| Maintainability | Concise, component-based | Verbose, nested tables |
| Development speed | Fast — fewer lines | Slower — more boilerplate |
| Output | Compiles to HTML | Already HTML |
Can I preview MJML emails online?
Yes. Paste your MJML into MailViewr and it compiles to HTML in your browser, then renders across Gmail, Outlook, Apple Mail, Yahoo and mobile devices — including dark mode — so you can see exactly how it looks before sending.
Does MailViewr convert MJML to HTML?
It does. MailViewr compiles MJML to email-ready HTML in the browser using the official MJML engine. You can preview the result, run a QA report, and download the generated HTML for any ESP.
Can I test MJML in Outlook?
Yes. After compiling your MJML, MailViewr previews the HTML in Outlook (desktop and mobile) alongside Gmail and Apple Mail, so you can catch Word-engine rendering issues before you send.
Is the MJML compiler free?
Completely free, with no signup or install. Open the editor, paste your MJML, and preview instantly.
Is my MJML uploaded or stored?
No. MJML is compiled entirely in your browser. Your source is never uploaded to a server just to preview it.
MJML vs HTML — which should I use?
MJML is faster to write and produces responsive, Outlook-safe HTML automatically, which is ideal for new builds. Hand-written HTML gives you the most control. MailViewr supports both — paste either and preview across clients.