Free email preview tool

Free dark mode email testing

MailMode is a free dark mode email testing tool for HTML, MJML and React Email. Paste or upload your email code and quickly compare light mode, dark mode, partial invert and full invert previews before running full inbox testing.

Start testing for free Learn how dark mode email testing works

Free to use
No sign-up required
Temporary share links

What you can test

Preview the source, modes and output that matter during build.

HTML

HTML email

Paste HTML directly, load a URL, or upload an HTML file to check light and dark previews.

MJML

MJML email

Render MJML into HTML and inspect the compiled output before sending it to a campaign tool.

React Email

Preview static React Email output in safe mode, then test the rendered HTML rather than only the source component.

Light + dark

Mode comparison

Compare light mode, authored dark CSS, partial invert and full invert simulations side by side.

Development sanity check

Use MailMode before full inbox testing.

MailMode is built for the fast middle of email QA: when you want to spot obvious dark mode problems, broken contrast, image issues, awkward inversion and risky email structure before spending time in heavier client testing tools.

It does not replace real inbox rendering suites such as Litmus or Email on Acid. It helps you catch problems earlier, so deeper client testing starts from a cleaner email.

Check light and dark previews while building.
Compare selective and aggressive inversion behaviours.
Review links, images, accessibility and tracking warnings.
Share a temporary preview with a client or teammate.

Shareable previews

Send a temporary preview link instead of a screenshot.

Share previews with clients or colleagues

Create a read-only hosted preview that keeps the same light, dark and inversion controls. Links are temporary, public to anyone with the active URL, and automatically expire after 3 days.

Read the shareable previews docs

Learn more

Learn more about email dark mode.

Honest limitations

Useful previews, not guaranteed inbox-perfect renders.

Dark mode behaviour varies by email client, app version, operating system and account type. MailMode provides fast preview and simulation modes to highlight likely issues, but important campaigns should still be tested in the real clients your audience uses.

FAQ

Free dark mode email testing questions.

Can I test HTML emails in dark mode for free?

Yes. MailMode lets you paste or upload HTML and preview dark mode behaviours for free with no sign-up required.

Does MailMode support MJML?

Yes. MailMode can render MJML into HTML so you can preview the compiled email in light mode, dark mode and inversion modes.

Does MailMode support React Email?

Yes. MailMode supports static React Email templates in safe preview mode so you can inspect the rendered email output.

Is MailMode a replacement for Litmus or Email on Acid?

No. MailMode is designed as a fast development sanity check, not a full inbox rendering suite. It helps spot obvious dark mode and inversion issues before deeper client testing.

Can I share a dark mode email preview?

Yes. MailMode can create temporary shareable preview links. Anyone with the active link can view the preview until it expires after 3 days.

What are partial invert and full invert modes?

They simulate common dark mode colour transformation behaviours where clients adjust backgrounds, text, borders and other colours.