Mozilla Firefox Icon System, Stroke Weights

In the Firefox icon system, we decided to use stroke weights with decimal values. According to specific visual rules and icon sizes, we used 1.25 px and 1.5 px strokes. In order to ensure the legibility of icons at small sizes, icon strokes with decimal numbers snap to the pixel grid just on one side. In addition, we implemented a special-cut spacing logic of 0.6 px for the 16 px icons 📐✨