Firefox 151 hides Snake easter egg in address bar calculator

Mozilla has embedded a playable Snake game inside Firefox's address bar calculator, a feature first appearing in Firefox 151. The easter egg activates only when a calculation entered in the address bar evaluates to exactly 150, such as 100+50, 15^2-75, or 75*2. Under normal circumstances, calculated results display with a copy-to-clipboard icon, but the special result of 150 causes a Firefox icon to appear instead, which opens a drop-down containing the game.

The browser joins a small tradition of hidden games in web browsers, following Google's Chrome dinosaur game and Vivaldi's built-in arcade offering. The Snake implementation uses keyboard arrow keys to control a Firefox-logo-headed snake that grows longer as it consumes dots, with collision detection against board edges and the snake's own tail ending the game.

How the Firefox address bar easter egg works

• Trigger condition: The easter egg activates exclusively when the address bar calculator feature produces a result of exactly 150, replacing the standard copy-value icon with a Firefox brand icon.
• Supported input formulas: Multiple mathematical expressions evaluate to 150, including 100+50, 15^2-75, and 75*2, suggesting the check occurs on the computed result rather than input pattern matching.
• Game mechanics: The Snake implementation uses standard keyboard arrow key input, with a Firefox-logo-headed sprite that grows tail length proportional to dots consumed, and failure conditions on wall or self-collision.
• Version availability: The feature is confirmed present in Firefox 151, indicating it was introduced in that release or earlier without documentation in release notes.
• UI integration: The game renders within a drop-down panel anchored to the address bar, leveraging existing browser chrome UI infrastructure rather than opening a separate page or tab.

Why it matters

While not a functional improvement, the easter egg demonstrates Mozilla's continued investment in browser personality and user delight at a time when Firefox faces sustained market share pressure from Chromium-based alternatives. For Linux distribution packagers and Firefox maintainers, this undocumented feature carries no packaging or dependency implications, though it may generate support queries from users discovering it accidentally through address bar calculations.