What is OKLCH? The perceptually uniform color space replacing HSL in modern CSS
OKLCH is the future of CSS colors. It's supported everywhere, perceptually superior to HSL, and enables programmatic color systems that actually look good. Start using oklch() in new projects today. The learning curve is small if you already understand HSL.
OKLCH (Lightness, Chroma, Hue) is a modern color space designed to be perceptually uniform, meaning that the same numerical change in a value produces roughly the same perceived change in color, regardless of the hue. This fixes HSL's biggest flaw: in HSL, a lightness value of 50% looks very different for yellow (bright) vs blue (dark).
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How this is calculated
OKLCH landed in all major browsers in 2023-2024 and is now safe for production use in 2026. The syntax in CSS is oklch(L C H) or oklch(L C H / alpha). L (lightness) ranges from 0 to 1 (or 0% to 100%). C (chroma) is the color intensity, typically 0 to 0.4 for screen colors. H (hue) is 0-360 degrees like HSL. The perceptual uniformity means you can generate entire color palettes mathematically: pick a hue, vary lightness and chroma, and every step looks evenly spaced. This is revolutionary for design system token generation.
Verdict
The syntax oklch(L C H) maps to lightness (0 to 1, or 0% to 100%), chroma (typically 0 to 0.4 for screen colors), and hue (0-360 degrees, same angle as HSL), so the mental model transfers from HSL in minutes. The structural upgrade is that the same numeric step produces the same perceived change across every hue, so an OKLCH palette generated by varying L and C at a fixed H looks evenly spaced where HSL's 50% lightness reads bright at yellow and dark at blue. Add the wide-gamut capability, OKLCH can express colors in Display P3 and Rec. 2020 beyond sRGB that the browser will clip or map, and the result is a token-generation tool that actually works for dark mode variants, accessibility-driven palettes, and HDR-aware CSS without re-tuning across hue ranges.