Color Contrast

Calculates the WCAG contrast ratio between a text color and a background color.

GET /check/contrast

Parameters

Parameter	Required	Description
text	Yes	Text (foreground) color as a hex value (e.g. #ffffff)
bg	Yes	Background color as a hex value (e.g. #000000)

Example

curl "https://api.uwuapps.org/check/contrast?text=%23ffffff&bg=%23000000"

Response

{
  "success": true,
  "textColor": "#ffffff",
  "bgColor": "#000000",
  "ratio": 21,
  "aa": {
    "normal": true,
    "large": true
  },
  "aaa": {
    "normal": true,
    "large": true
  }
}

Response fields

Field	Description
ratio	WCAG contrast ratio (1:1 to 21:1)
aa.normal	Passes WCAG AA for normal text (ratio ≥ 4.5)
aa.large	Passes WCAG AA for large text (ratio ≥ 3.0)
aaa.normal	Passes WCAG AAA for normal text (ratio ≥ 7.0)
aaa.large	Passes WCAG AAA for large text (ratio ≥ 4.5)

WCAG thresholds

Level	Normal text	Large text
AA	4.5:1	3.0:1
AAA	7.0:1	4.5:1

Large text is defined as 18pt (24px) or 14pt bold (approximately 18.67px bold).

Notes

• Colors must be hex format: #rgb, #rrggbb, or without the # prefix.

• The ratio is the same regardless of which color is text or background.