Encode and decode Base64, base64url and MIME with UTF-8-safe text for Arabic and emoji
Color Picker & WCAG Contrast
Convert a colour between HEX, RGB, HSL, HSV, CMYK, LAB and OKLCH, compute the WCAG 2.x contrast ratio with AA and AAA verdicts, and generate a 50–900 scale and colour harmonies.
Workspace
Contrast (WCAG 2.x)
Colour scale
Harmonies
How the result is calculated
Formulas are computed from sRGB values: HSL and HSV by the standard equations, CMYK by the naive method (K = 1 − max), LAB from XYZ with a D65 white point, and OKLCH via OKLab (Ottosson matrices). Contrast follows WCAG 2.x: (L1 + 0.05) ÷ (L2 + 0.05) where L is relative luminance after linearizing sRGB; thresholds are AA = 4.5:1 for normal text and 3:1 for large, and AAA = 7:1 and 4.5:1. The scale mixes the colour with white or black, and harmonies rotate the HSL hue.
Limits:
CMYK is approximate without an ICC profile and does not match print. The WCAG 2.x ratio has known limits (it does not distinguish light from dark precisely) and APCA is not implemented. Alpha values and newer CSS forms (color()) are not supported. Colour-blindness simulation and the screen eyedropper are not included.
FAQ
What is the minimum contrast?
4.5:1 for normal text and 3:1 for large text (AA).
Why does CMYK differ from my printer?
It is a mathematical conversion without a printer colour profile.
