Dark Mode Email Tester

Catch dark mode rendering bugs before subscribers do.

A free dark mode email tester that simulates how Apple Mail, Outlook, and Gmail invert your colors. Run a dark mode test on any HTML email and auto-flag contrast failures — no signup, browser-based.

Ready to run a dark mode test

Upload your HTML email or paste it in to simulate how it renders in dark mode across Apple Mail, Outlook, and Gmail.

Dark mode is no longer optional — and most emails fail it

More than 50% of email opens happen on devices with dark mode enabled. Apple Mail, Outlook for Mac, Outlook.com, and Gmail (mobile + select web themes) all force some flavor of color inversion on the emails they show. Without dark mode testing, the white logo you spent hours perfecting can disappear into a now-white background, your CTA can blend into its container, and dark grey body text can become unreadable on a near-black background.

EMLinter's dark mode email tester runs an aggressive simulation — the same inversion math Outlook for Mac applies — so you see worst-case rendering up front. The Analyze Colors feature walks every text node in your email, calculates light-mode and dark-mode contrast ratios, and flags any pair that fails WCAG AA in either state. Then it suggests a universal color that passes both.

Dark Mode Email Tester FAQs

A dark mode email tester simulates how your HTML email renders in dark-mode inboxes — iOS Mail, Apple Mail, Outlook for Mac, and Gmail mobile. Many clients automatically invert backgrounds and adjust text colors, which can make logos disappear, text become unreadable, or CTAs blend into the background. Dark mode testing lets you catch and fix these issues before you send.
Upload or paste your HTML, then toggle the dark/light switch. The tool applies the same CSS filter transformation that Outlook for Mac and certain Gmail dark themes use — inverting backgrounds while preserving image colors. You see your email exactly as a subscriber on dark mode would.
Three behaviors exist: (1) Apple Mail and iOS preserve your colors but invert white backgrounds; (2) Outlook for Windows/Mac and Outlook.com fully invert your color palette unless you opt out; (3) Gmail (mobile and some web themes) partial-invert mostly white-on-white designs. Our dark mode test simulates the aggressive option so you see worst-case rendering.
Use the Analyze Colors button to surface every text/background pair that fails WCAG AA contrast in either light or dark mode. The tool suggests universal colors that pass both. You can also add the meta tag <meta name="color-scheme" content="light dark"> and a @media (prefers-color-scheme: dark) block to give clients explicit guidance.
No directly — but it affects engagement, which indirectly affects deliverability. Unreadable dark-mode emails get low click-through and high delete-without-open rates, both of which hurt your sender reputation over time. Testing is preventive.
Completely free, no signup, no uploads. The simulator runs entirely in your browser using a sandboxed iframe — your HTML is never sent to a server. The color contrast analysis also runs client-side.