What alt text is
Alt text (alternative text) is a written description attached to an image in the HTML:
<img src="brew-setup.jpg" alt="Mason jar of cold brew steeping next to a kitchen scale" />
It's invisible in normal browsing. It appears when the image fails to load, it's what screen readers speak aloud to blind and low-vision visitors, and it's the primary way search engines understand what an image shows.
Why it matters
Three separate audiences read it:
- Google. Crawlers don't "see" images the way people do — alt text is the described content they index. It's how images earn a place in Google Images, and it adds context to the page itself. Google's image SEO guidance lists alt text as its primary recommendation.
- Visitors using screen readers. For them the alt text is the image. Missing alt text reads as a filename or as silence — a real accessibility failure, and in many jurisdictions a legal-compliance one.
- Anyone on a bad connection. Broken image? The alt text still communicates.
Writing good alt text
Describe what the image shows, specifically, in about a sentence:
- Weak:
alt="coffee" - Better:
alt="Cold brew concentrate being poured over ice"
A few rules that cover most cases:
- Be specific, stay honest. Describe this image, not the topic you wish it illustrated.
- Don't keyword-stuff.
alt="cold brew best cold brew coffee cold brew recipe"is spam to Google and gibberish to a screen-reader user. - Skip "image of" / "picture of". Everyone already knows it's an image.
- Purely decorative images (background flourishes, spacers) should have an empty alt
attribute —
alt=""— so screen readers skip them. Empty on purpose is correct; missing is not.
The filename helps too
brew-setup.jpg supports the alt text; IMG_4832.jpg says nothing. Descriptive filenames and
alt text together give search engines a consistent story about the image.