Every color format in CSS ultimately describes the same thing — a point in color space — but they disagree on which coordinates to use, and that choice affects how intuitively you can predict what tweaking a number will do. HEX and RGB have been the default for decades, HSL made hue/saturation/lightness edits more intuitive, and OKLCH is the newest entrant, designed to fix a real problem the other three share.
HEX and RGB: how the display actually stores color
#4f46e5 is just RGB in hexadecimal — each pair of hex digits is one channel (red, green, blue) from 0-255. RGB maps directly onto how a screen's pixels are physically lit, which makes it fast and universal, but it's a poor format for a human to reason about: there's no direct way to look at #4f46e5 and #6366f1 and know which is "lighter" or by how much, since lightness is smeared across all three channels at once.
HSL: hue, saturation, lightness — a step toward intuition
HSL re-parameterizes the same RGB color space as a hue angle (0-360°), a saturation percentage, and a lightness percentage — much closer to how people actually describe color ("a brighter blue", "less saturated"). That's a real improvement for hand-tuning a single color. The catch: HSL's "lightness" doesn't match human perception consistently across different hues. A pure yellow and a pure blue at the same HSL lightness value do not look equally bright to the human eye — yellow reads as noticeably lighter. That mismatch causes real problems building a color scale or gradient: stepping lightness evenly in HSL produces a scale that doesn't look evenly stepped.
OKLCH: perceptually uniform lightness
OKLCH (Lightness, Chroma, Hue in the OKLab color space) was designed specifically to fix that mismatch: its lightness axis is built to match how humans actually perceive brightness, across every hue. Two OKLCH colors with the same L value look equally light to a human viewer, regardless of whether one is yellow and the other is blue. That property — perceptual uniformity — is what makes OKLCH noticeably better for generating a color scale (a design system's 50-900 shade ramp), an accessible gradient, or programmatically adjusting a brand color's lightness without it looking subtly "off" at certain hues. OKLCH also natively supports a wider gamut than sRGB (P3 and beyond), which HSL and 6-digit HEX cannot represent at all.
When OKLCH is worth switching to
- Generating a shade scale (a color's 100/200/300.../900 variants) — stepping OKLCH lightness evenly gives a visually even scale; the same approach in HSL does not.
- Building or checking contrast-sensitive UI — since OKLCH lightness tracks perceived brightness, it's a better predictor of legibility than HSL lightness (though it's still not a substitute for an actual WCAG contrast-ratio check against real background/foreground pairs).
- Targeting wide-gamut displays — OKLCH can express P3 colors that are more vivid than anything representable in HEX/RGB/HSL.
For a one-off color pick, or a codebase that already has an established HEX/HSL-based design system, there's no urgency to migrate — HEX and HSL remain perfectly valid, universally supported CSS. OKLCH earns its keep specifically around palette generation and gradients, where perceptual uniformity actually changes the output.
Try it yourself
Convert a color between HEX, RGB, HSL, and OKLCH with our Color Converter — it also includes a live swatch preview and a WCAG 2 contrast-ratio checker against AA/AAA thresholds. Note that its conversions target the sRGB gamut: an OKLCH value outside sRGB (true wide-gamut P3 territory) gets clamped to the nearest in-gamut color rather than preserved, so it's the right tool for everyday sRGB color work, not for round-tripping colors that genuinely need P3 or wider. Runs entirely in your browser.