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. 5 free previews, 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, 5 free previews before 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 install required. Open the editor, paste your MJML, and preview instantly — 5 free previews before signup.
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.