Alt Text for SEO

Alt text is the written alternative to an image, stored in the alt attribute of the HTML img element: <img src="tram.jpg" alt="Yellow tram climbing a cobbled street">. Screen readers speak it, browsers display it when the image fails, and crawlers read it.

Technically it’s an attribute, not a tag, which is why you’ll see “alt attribute SEO” in technical docs and “alt tag SEO” almost everywhere else. Both mean the same thing. Whether someone searches for alt tags SEO tips or talks about SEO alt tags, they mean writing that attribute well.

Short answer: yes, as one signal. Google’s image guidelines say it uses alt text together with computer vision and the surrounding page to work out what an image is about.

The effect is clearest in image search, where a picture needs words attached to rank at all. On a regular results page, alt text supports the page’s topic rather than ranking it by itself. The link between alt text and SEO is also indirect: accessible pages are easier to use, and alt text is part of that.

What alt text won’t do is rescue thin content or rank a page for terms it doesn’t cover. Using alt tags in SEO works when they describe real images on a page that is already about the topic.

Keyword stuffing in alt text looks like alt="banana bread banana bread recipe easy banana bread". It reads as spam to people using screen readers, and Google’s guidance lists it as something to avoid.

A useful test: read the alt text aloud to someone who can’t see the image. If it sounds like a description, it’s fine. If it sounds like a list of search terms, rewrite it. Image alt text SEO is about matching words to the picture, not adding as many as possible.

Our alt text checker flags repeated keywords, keyword lists and generic words in alt text you already have.

Not every image needs words. Dividers, background textures and purely ornamental icons should have an empty alt attribute: alt="". That tells screen readers to skip the image. Don’t delete the attribute: without it, some screen readers fall back to reading the file name aloud.

If a decorative-looking image is also a link, it isn’t decorative any more: its alt text should say where the link goes.

Alt text works alongside a few other signals Google mentions in its image guidance:

• Descriptive file names. yellow-tram-lisbon.jpg says more than IMG_4031.jpg.
• Nearby text. Captions and the paragraph around an image help explain it.
• Placement. Put important images near the text they relate to, and use real img elements rather than CSS backgrounds for content images.
• Size and speed. Compressed, correctly sized images load faster for everyone.