Best Free Online Developer Tools to Use in 2026
A practical, opinionated list of the best free online developer tools worth using in 2026, organized by category so you can find what you need fast.
Aug 08, 2026
WCAG Color Contrast Checker
Check foreground/background color contrast ratio against WCAG 2.2 AA/AAA compliance levels with pass/fail indicator.
Color Contrast Checker
--.--
: 1
AA Normal
--
≥ 4.5:1
AA Large
--
≥ 3:1
AAA Normal
--
≥ 7:1
AAA Large
--
≥ 4.5:1
Sample Text — The quick brown fox jumps over the lazy dog.
Small text sample for visual reference. WCAG requires 4.5:1 for normal text and 3:1 for large text (≥18pt or ≥14pt bold).
- Enter colors — Type hex codes (e.g. #111827) or use the color picker for foreground (text) and background colors.
- Check results — The contrast ratio is calculated instantly. Each WCAG level shows PASS or FAIL.
- Swap colors — Use the Swap button to quickly invert foreground and background.
- Preview — Sample text is rendered with your chosen colors for visual reference.
WCAG 2.2 Contrast Requirements
| Level | Normal Text | Large Text | Description |
|---|---|---|---|
| AA | ≥ 4.5:1 | ≥ 3:1 | Minimum contrast for readability |
| AAA | ≥ 7:1 | ≥ 4.5:1 | Enhanced contrast for better accessibility |
Large text is defined as ≥18pt or ≥14pt bold. These criteria apply to text and images of text, excluding logos and decorative elements.
What is the WCAG contrast ratio?
The contrast ratio is a measure of the difference in luminance between two colors, ranging from 1:1 (identical) to 21:1 (black on white). WCAG defines minimum ratios for accessible text.
How is the contrast ratio calculated?
The relative luminance of each color is calculated using the sRGB formula, then the ratio is (L1 + 0.05) / (L2 + 0.05) where L1 is the lighter color's luminance. This follows the WCAG 2.x specification.
What is the difference between AA and AAA?
AA is the minimum compliance level required by most accessibility standards (e.g., Section 508). AAA is a higher standard that provides enhanced readability for users with visual impairments.
Is my data sent to a server?
No. All calculations happen 100% client-side in your browser. Your colors never leave your device.
Last updated: 17 Aug 2026
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