Color contrast and readability checker

Readability is the luminance difference between the text color and the background color. The greater the difference, the easier it is to read the text. Too low contrast makes content hard to read - especially for people with vision impairments, older adults, or in difficult lighting conditions (e.g., on a phone in direct sunlight).

According to the World Health Organization (WHO), approximately 2.2 billion people worldwide have some form of vision impairment. In addition, millions have color blindness (about 8% of men and 0.5% of women), and many more experience age-related vision decline.

The tool calculates the contrast ratio using the formula specified in the WCAG 2.1 (Web Content Accessibility Guidelines) - international digital accessibility guidelines. The result allows an objective assessment of whether colors are readable enough, regardless of monitor settings or individual color perception.

The tool shows the contrast ratio on a scale from 1:1 (no contrast) to 21:1 (maximum contrast - black on white). The result is compared against thresholds defined in the WCAG standard:

• Normal text - requires at least 4.5:1 for Level AA (minimum standard) or 7:1 for Level AAA (enhanced standard). Applies to text under 18pt (24px) or under 14pt (18.5px) bold.
• Large / bold text - requires at least 3:1 for Level AA or 4.5:1 for Level AAA. Applies to text from 18pt (24px) or from 14pt (18.5px) bold - headings, buttons, highlights.
• Icons and UI elements - require at least 3:1 for Level AA. Applies to icons, buttons, form fields, and other interface elements that convey information.

Level AA is the minimum required by digital accessibility regulations in many countries, including the EU Web Accessibility Directive. Level AAA provides better readability but is not always practical to achieve for all elements.

If contrast is too low, you don't need to search for the right color by trial and error. The Match feature automatically finds a text color variant that meets the selected contrast threshold.

How matching works:

1. Select the matching target from the list - e.g., AA for normal text or AAA for large text.
2. Click the Match button.
3. The tool will search through lightness variants of the text color and suggest the closest one that meets the requirements.
4. The suggested color can be copied to the clipboard or immediately set as the new text color.

The algorithm preserves the hue and saturation of the original color, changing only the lightness. The suggested color stays consistent with the visual identity while meeting the accessibility standard.

Color blindness affects about 8% of men and 0.5% of women. People with color blindness may have difficulty distinguishing certain color pairs, even if the luminance contrast is sufficient.

Most common types of color blindness:

• Deuteranopia - difficulty distinguishing green and red (most common form)
• Protanopia - difficulty seeing red
• Tritanopia - difficulty seeing blue and yellow (rare)

This tool checks luminance contrast, which is important for all users. However, when designing, it is also worth avoiding problematic color combinations (e.g., red text on a green background) and not relying solely on color to convey information - use shapes, icons, and text as well.