How to check dark-mode and mobile previews?

Dark mode testing requires specialized tooling because dark mode behavior varies significantly across clients. Litmus and Email on Acid now offer dark mode previews for major clients, showing how your email transforms when the system inverts colors. These automated previews catch the most common issues: inverted images, unreadable text, and disappearing elements. However, automated tools don't catch every nuance. The uexact shade of your brand color inverted may only be obvious on an actual device.

For mobile previews, automated tools provide useful approximations, but physical device testing remains valuable for critical campaigns. The simulation of a 375px viewport doesn't capture real-world factors: how the email loads on slow connections, how images appear on high-DPI screens, or how touch targets feel in actual use. Keep test devices-at minimum, one current iPhone and one Android device-for final verification.

Build a testing matrix that matches your audience: if 40% of opens happen on iPhone in dark mode, that combination needs attention. Test both iOS and Android native mail apps plus Gmail's mobile app. They ubehave differently. Dark mode and mobile aren't edge cases anymore; they're primary viewing contexts. Test accordingly, or accept that half your audience sees something you never reviewed.