Dark mode behavior varies by email client and cannot be controlled consistently by Firstup.

Some email clients do not support dark mode for emails. Others automatically adjust email colors, but the exact behavior differs by client, device, and settings. As a result, an email may appear differently to recipients using dark mode.

Expected Dark Mode Variations

Common examples include:

• Gmail on the web: Does not support dark mode for email content.
• Proton Mail: May fully invert email colors.
• Outlook: May partially invert colors.
• Apple Mail: Applies dark mode behavior based on the email’s CSS and may fully invert certain content.

Because these behaviors are determined by the recipient’s email client, Firstup cannot reliably control or guarantee the final appearance of an email in dark mode.

Consider Visual Assets

Images, logos, QR codes, and other visual assets can display differently in dark mode. Consider how branded visuals, transparent images, light-colored logos, and high-contrast designs will appear against both light and dark backgrounds.

For example, a dark logo with a transparent background may become difficult to see if an email client changes the surrounding background to a dark color. QR codes should also maintain sufficient contrast to remain scannable.

Use Dark Mode Preview as a Guide

The dark mode preview in Firstup is intended as a previewing aid only. It does not control or guarantee how an email will render in recipients’ inboxes.

Test Important Emails

For important communications, test your email across the devices and email clients used by your audience. Testing is especially important when your email includes branded visuals, logos, QR codes, or high-contrast designs.