Dark / Light Theme Toggle

Preview how a web page or HTML email looks in dark and light mode without changing your operating system's theme. Many sites and HTML emails use the CSS media query @media (prefers-color-scheme: dark) to show a dark design. This extension lets you force that dark or light design on the current tab with one click, which is useful for reviewing email proofs (for example in Workfront web proofing), QA testing and design reviews. WHAT IT DOES • Click the toolbar button to switch the current tab between dark (moon icon) and light (sun icon). • Right-click the button to choose Force dark, Force light or Reset to system theme. • Keyboard shortcut: Alt+Shift+D (can be changed at chrome://extensions/shortcuts). • Works inside iframes, including cross-origin ones such as proofing viewers and email previews. • Keeps working on styles and frames that load after you click. • Applies to one tab only; other tabs keep your normal theme. • Remembers the choice for that tab while it's open, including after a reload. • No debugging banner and no changes to Chrome or OS settings. WHAT IT DOES NOT DO • It does not invert colours or create a dark mode for pages that don't have one. It only switches between the light and dark styles the page already has. • It does not imitate how email clients apply their own dark mode (such as Gmail app inversion or Outlook colour rewriting). Use a dedicated email testing service for that. • It cannot change stylesheets loaded from another site that blocks cross-origin access. HTML emails, which keep their styles in <style> blocks, are not affected by this. • It does not change what JavaScript sees when a page checks the theme in code (window.matchMedia). Pages that switch themes with JavaScript instead of CSS won't change. • It does not work on chrome:// pages, the Chrome Web Store or other pages Chrome protects. • It does not collect, store, send or sell any data. There are no analytics, no accounts and no network requests. HOW IT WORKS When you click the button, the extension finds the page's prefers-color-scheme rules and makes the chosen theme's rules always apply. Choosing "Reset to system theme" restores the original rules exactly.