The tool converts your hex color to HSL (Hue, Saturation, Lightness), then holds the hue and saturation fixed and swaps in a different lightness value for each step from 50 up to 950, 50 apart - lower numbers are lighter, higher numbers are darker. Because only lightness changes, every shade in the scale is recognizably the same color, just lighter or darker - useful for building a consistent design system, chart series, or UI theme from one brand color. The red arrow marks the swatch closest to the color you picked.