If Windows is on Light mode, Firefox may copy that.

This tends to happen sometimes after Windows updates. Firefox can reset or start following the system theme again, which is why your search/address bar suddenly looks light instead of dark. A few quick things you can try: First, set Firefox to Dark mode manually * Open the menu => Settings * Scroll to "Language and Appearance" * Set "Website Appearance" to "Dark" * In "Themes", make sure "Dark" is selected (not “System”) Also check your Windows settings * Go to "Settings => Personalization => Colors" * Make sure it’s set to "Dark" If Windows is on Light mode, Firefox may copy that. If the rest is dark but the search bar is still white This can be a small glitch. Try: * Settings => General => Performance * Uncheck “Use recommended performance settings” * Turn off hardware acceleration * Restart Firefox In most cases, just switching Firefox from “System theme” to the "Dark theme" fixes it and keeps it from changing again after updates. If it still keeps happening, it might be worth checking if an add-on or theme is interfering, but usually the steps above sort it out.