Designing for Accessibility: Best Practices

Start with contrast

Contrast ratios compare the brightness of two colors, such as text and its background. The scale runs from 1:1, which means no difference at all, up to 21:1 for black on white. A widely used set of web accessibility guidelines sets common targets at its standard conformance level:

At least 4.5:1 for normal-size text.
At least 3:1 for large text, generally meaning around 18 point regular or 14 point bold and above.
At least 3:1 for meaningful interface parts, such as input borders, icons that carry meaning, and the outlines of buttons.

Logos and purely decorative elements are generally exempt. These numbers are minimums, not goals. Text that only just passes can still be tiring to read, especially on small screens or in bright light.

You do not need to calculate ratios by hand. Contrast checkers, usually built into design and browser tools, take two colors and report the ratio. The practical habit is to check any pairing you are unsure about, especially light gray text, text over photographs, and colored buttons with white labels. Underneath it all is the same idea as color contrast in general: differences in lightness are what make shapes readable.

Text over images is a frequent trouble spot, because the background changes under the letters. Common fixes include placing text on a solid or semi-opaque panel, darkening the image under the text, or choosing a calmer part of the photo. Whatever you pick, check the lightest and darkest areas the text touches.

Make text readable

Contrast is only part of legibility. A few other choices help:

Size. Body text on screens is often set around 16 pixels or larger. Very small captions and legal text are the usual offenders. Building a coherent type scale keeps the smallest size from drifting too low.
Weight and shape. Extremely thin strokes vanish at small sizes. Choose letterforms with clear differences between characters, such as a capital I, a lowercase l and the number 1.
Line length and spacing. Lines that are too long or tightly packed are hard to track. Comfortable line spacing and moderate line length help many readers, including those with dyslexia or low vision.
Alignment. Left-aligned text with a ragged right edge is often easier to read than fully justified text, which can create uneven gaps.
Scaling. People enlarge text through browser or device settings. Layouts should still work when text grows, rather than clipping or overlapping.

Do not rely on color alone

Color is a strong signal, but not everyone perceives it the same way, and it can disappear in grayscale printing or on a poorly calibrated display. A rule of thumb is that color should never be the only way to communicate something.

A form error should include a message and an icon, not just a red border.
A chart with several lines should use labels, patterns or different line styles, not only different hues.
A link inside body text is easier to spot when it is underlined or otherwise distinguished by more than color.
A status such as “complete” or “failed” should say so in words.

A quick test is to view your design in grayscale. If it still makes sense, you are in good shape. Color blindness is the best-known reason, though glare, small screens and printing can cause similar trouble.

Write useful alt text

Alt text is a short written description of an image, used by screen readers and shown when an image fails to load. Good alt text describes what the image contributes, not everything visible in it.

A photo that illustrates a point should be described in a phrase or sentence that conveys that point.
A chart needs its key finding stated in text nearby or in the description.
A decorative flourish should have an empty alt attribute, so assistive tools skip it.
Skip phrases like “image of” or “picture of”, since the tool already announces that it is an image.
Text inside images is a problem in itself. If a banner includes words, those words should also exist as real text or in the alt description.

Context decides the right description. The same photo of a person might need their name in one place and their action in another. Good data visualization also gives the main takeaway in plain words, so it does not rest on the graphic alone.

Build for the keyboard

Many people navigate without a mouse, either by choice or necessity. A keyboard-friendly layout allows them to do everything a mouse user can do.

Logical order. Pressing the tab key should move through elements in an order that matches the visual reading flow.
Visible focus. There must be a clear outline or highlight showing which element is currently selected. Removing the focus outline for looks is a common mistake.
No traps. A user who tabs into a menu or pop-up must be able to leave it.
Skip links. A hidden-until-focused link that jumps past repeated navigation saves keyboard users many key presses.
Real controls. Buttons and links built with the standard elements usually work with keyboards and screen readers automatically. Custom replacements need extra care.

Clear website navigation and a sound page structure make all of this easier.

Size and space for touch

Touch targets should be large enough to hit without precision, with space around them so neighboring actions are not triggered by accident. A frequently cited guideline range is roughly 44 to 48 pixels square for tap targets, though recommendations vary by platform. Gestures that need fine control, like dragging or pinching, should have a simpler alternative.

Handle motion and media with care

Avoid content that flashes more than a few times per second.
Let people pause, stop or hide moving content such as carousels and background video.
Respect device settings that ask for reduced motion.
Provide captions for video and transcripts for audio.
Avoid auto-playing sound.

Use headings and plain language

Real headings, in a logical order, make a page navigable by screen reader and easier to scan visually. A clear visual hierarchy should match the underlying structure. Use descriptive link text such as “Download the price list” instead of “Click here,” since screen reader users often browse a list of links on their own.

Test the work

No single check catches everything. Combine automated checkers, which find missing alt text and low contrast, with manual passes: tab through the page, zoom to 200 percent, view in grayscale and read it aloud. Where possible, include people with disabilities in testing. Treat each issue as an ordinary design bug rather than a special case, and keep a short checklist so that these practices become routine. Standards and legal expectations vary by country and sector, so confirm the requirements that apply to your project.