Color Contrast Checker is an offline desktop accessibility studio for UI designers and frontend developers on Linux. Built around exact sRGB linearization and WCAG 2.1 relative luminance calculations, it helps verify text and component legibility, auto-fix failing foreground colors, audit entire brand palettes, and export ready-to-use design tokens.

Key Features:

• WCAG 2.1 Contrast Ratio & Auto-Fix: Computes exact sRGB relative luminance and (L1 + 0.05) / (L2 + 0.05) contrast ratios with AA Normal (4.5:1), AAA Normal (7.0:1), AA Large (3.0:1), and UI Component (3.0:1) badges, synced HSL sliders, one-click lightness auto-fix for AA/AAA compliance, and a live Button, Card, and Form UI preview.
• Full Palette Contrast Matrix: Edit 4 to 8 brand hex colors and inspect an interactive N x N accessibility grid highlighting every compliant foreground/background pair, with support for loading local GIMP .gpl, CSS, and JSON palette files.
• Harmonies & Palette Exporter: Generates Complementary, Analogous, Triadic, and Split-Complementary color scales and exports CSS custom properties, Tailwind config snippets, GIMP .gpl palettes, structured JSON, and CSV accessibility matrices.

Disclaimer: Color Contrast Checker is an independent open-source project by TC Studio and is not affiliated with, endorsed by, or sponsored by Coolors.