unflashbang — designbystephen

Stops the blinding white flash dark-theme users get from new tabs, about:blank, and unstyled/loading pages — without asking for access to your browsing data.

unflashbang works by using Firefox's own built-in dark content color scheme setting (browserSettings.overrideContentColorScheme) instead of injecting a content script into every page you visit. This is the same mechanism behind the manual about:config dark-mode tweak, just exposed as a supported API — it changes a browser preference, not your page content.

What it does:
• Applies Firefox's dark content color scheme everywhere, so unstyled pages, about:blank, and loading screens get a dark default background, scrollbars, and form controls instead of flashing white.
• Replaces the New Tab page with a local, zero-network dark page — nothing to flash because nothing loads over the network.
• Optional "Fix this tab now" button in the toolbar popup for the rare stubborn page: it requests a one-click, single-tab activeTab permission at the moment you click, injects one CSS rule into just that tab, and nothing persists after reload.
• Switch between Dark, Light, or Match system at any time from the popup or the full options page.

Permissions: only browserSettings, storage, and scripting (an inert API gate until you click "Fix this tab now"). No <all_urls>, no host permissions, no persistent content scripts, no access to your browsing data.

Known limitations: pages are reported as light-themed regardless of this setting when privacy.resistFingerprinting is on (by design, to prevent theme-based fingerprinting), and Firefox's "Use system colors" setting can also force white independently of any extension. "Fix this tab now" is the fallback for both.