Alt text

Alt text serves three distinct audiences: screen readers (which read the alt text aloud when navigating an image), search engines (which use alt text as a signal of what the image and surrounding page are about), and users with broken images (when the alt text displays instead of the missing image).

Good alt text describes the image. 'A red 1968 Ford Mustang convertible parked on Pacific Coast Highway at sunset' is descriptive; 'image1.jpg' is not; 'A car' is too vague. The right length is typically 5–15 words — long enough to describe the image, short enough that a screen reader user doesn't lose patience.

Decorative images (purely visual flourishes that don't add meaning) should have alt='' (empty alt). Empty alt signals to screen readers that the image can be skipped. Setting alt='decorative image' is the wrong pattern — it forces the screen reader to announce 'decorative image' for every flourish.

Functional images (icons that act as links or buttons, like a search-icon button) should describe the function, not the visual. <img src='search.svg' alt='Search'> is right; <img src='search.svg' alt='Magnifying glass icon'> is wrong because it describes the icon's visual rather than what the user is about to do.

Common mistakes: missing alt entirely (most damaging — screen readers fall back to filename), keyword-stuffed alt ('AI website builder AI website builder generate site fast AI builder' triggers Google's spam detection), and identical alt text across many images (signals a templated, unoptimized site). Modern AI builders generate alt text by default; the output still needs review for accuracy.