Image Formats and Accessibility: What You Need to Know

Image formats themselves do not affect accessibility, but how you use images does. Alt text, semantic HTML, and careful format choice make images accessible.

Alt Text is Essential

Every image needs descriptive alt text. Screen readers read alt text to blind users. Format is irrelevant; alt text is everything.

Alt Text Best Practice

Descriptive: "red Ferrari 458 Italia parked on street". Avoid: "image" or "photo". Answer: "What would I say if describing this image to someone over the phone?"

Figure and Figcaption

Use <figure> and <figcaption> for images with captions. Screen readers announce the relationship between image and caption.

Decorative Images

Pure decorative images (bullets, dividers) should have alt="". Empty string tells screen readers to skip.

Format and Quality

Use clear, legible images. Avoid tiny text overlays. Convert to formats that preserve quality (PNG for graphics, WebP for photos) to maintain readability.

Color Contrast

If text is in the image, ensure sufficient contrast (4.5:1 ratio per WCAG). Format does not matter; content clarity does.

Responsive Images and Accessibility

Srcset and picture elements are transparent to screen readers. Use the same alt text on all variants.

Image-Heavy Content

Articles with many images need transcripts or detailed captions for visually impaired users. Format is secondary to content.

Testing

Test with screen reader (NVDA on Windows, VoiceOver on Mac/iOS). Listen to how alt text is read. Verify context is clear.

Tools and Resources

WAVE browser extension detects accessibility issues. WCAG 2.1 Level AA is the standard. Alt text analyzer tools verify descriptions are sufficient.