Is it possible for a gradient between accessible colors to also be accessible?

Ensuring accessibility on websites is a top priority for me, with our goal being at least AA standard. We utilize tools like and to test the contrast between background colors and black or white text.

For example, let's consider white (#fff) text at a font size of 18px. Color one: #546FAF has a contrast ratio of 4.92 Color two: #B349B1 has a contrast ratio of 4.66

If I were to create a linear gradient between these two colors as a background, would white text at 18px remain accessible? I've attempted to choose colors close to the text during the gradient transition, but I'm hopeful that it will never fall below the 4.5 ratio threshold.

Thank you!

Answer №1

If both of your chosen colors pass contrast ratio tests, you will indeed be safe. However, this is only applicable when using white on a darker gradient background, as per your indication. It's important to note that for dark colors on a gradient background, the opposite holds true.

When gradients with two equal (or nearly equal) luminance values are combined, they tend to result in a slightly lower luminance value in the middle.

The contrast between two colors is determined by luminance, calculated using the following formula:

(L1 + 0.05) / (L2 + 0.05)

where L1 represents the relative luminance of the lighter color,

and L2 is the relative luminance of the darker color.

Due to gradients darkening in the middle with similar luminance values, the contrast ratio increases towards the center (L2 decreases as it approaches black, while L1 remains constant). This leads to all colors falling above the threshold, with greater contrast towards the central area.

However, if a dark color is used as the foreground color, the contrast ratio will decrease as the gradient darkens in the middle (L2 remains constant, but L1 decreases).

Answer №2

Do you have bold text in your content? If so, the minimum color contrast requirement would need to be adjusted to 3:1 due to the larger size of bold text (18px+).

Webaim defines large text as being 14 point (typically 18.66px) and bold or larger, or 18 point (typically 24px) or larger.

You may already be familiar with contrast checkers, but it's worth mentioning that there are tools available that can assess the accessibility of text on gradient backgrounds. One such tool is Accessibility Insights for Web by Microsoft, which features a Fastpass function that provides instant feedback on contrast levels.

Ultimately, the goal of these guidelines is to ensure accessibility for all users. Even if a design meets the numerical thresholds recommended by automated tools, it's essential to consider real-world readability. For example, while designs on csszengarden.com may pass automated checks, they may still pose challenges for some users.

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