About · Methodology · Standards

Last updated 2026-07-11 · This page documents the tool's trustworthiness (E-E-A-T).

What this tool is

The WCAG Color Contrast Checker takes a foreground (text or graphic) color and a background color and reports the WCAG 2.1/2.2 contrast ratio, whether it passes AA and AAA for normal text, large text and UI elements, a live rendered preview, and the nearest passing color. It is free, needs no signup, and runs entirely in your browser — nothing is uploaded.

How it computes results

• Color parsing: HEX (#RGB, #RRGGBB, with or without #, alpha ignored), rgb()/rgba(), and hsl()/hsla().
• Relative luminance: each sRGB channel is linearized (c/12.92 when c ≤ 0.03928, else ((c+0.055)/1.055)^2.4) and combined as L = 0.2126R + 0.7152G + 0.0722B.
• Contrast ratio: (L1 + 0.05) / (L2 + 0.05), with L1 the lighter luminance.
• Thresholds: AA 4.5:1 / AAA 7:1 (normal), AA 3:1 / AAA 4.5:1 (large), 3:1 (UI, SC 1.4.11). A pass requires the ratio to be at or above the threshold.
• Suggestions: the foreground's hue and saturation are held constant while its HSL lightness is scanned to find the closest color meeting the target ratio.

Standards followed

• WCAG 2.1 — Relative luminance: w3.org/TR/WCAG21
• WCAG 2.1 — Contrast ratio: w3.org/TR/WCAG21
• SC 1.4.3 Contrast (Minimum, AA), 1.4.6 Contrast (Enhanced, AAA), 1.4.11 Non-text Contrast (AA)

Limitations

• Uses the WCAG 2.x algorithm, not the WCAG 3 draft (APCA).
• Alpha/transparency is ignored — flatten semi-transparent colors against their backdrop first.
• Suggestions change lightness only; some targets need a different hue or background.
• An automated ratio is necessary but not sufficient — test real interfaces with assistive tech.

Privacy

Colors are never sent to a server. Inputs are stored only in your browser (localStorage) and in the optional share link (?s= token). There is no account and no tracking beyond the site's ads and aggregate analytics.

Who runs it

• Operator: bal.pe.kr (an individual micro-SaaS portfolio)
• Contact: comsamo84@gmail.com
• More tools: bal.pe.kr/tools