Alt Attribute SEO

The alt attribute is an HTML property you add to an <img> tag. It serves two audiences: search engines and people using screen readers. When an image fails to load, the alt text appears in its place. For someone using a screen reader, that text is what gets spoken. Search engines read it too, but they do not treat it as a direct ranking signal. I have seen plenty of pages rank well with no alt text, and pages with perfect alt text that rank nowhere. So why bother? Because alt text contributes to image search visibility and helps reinforce the page's topical relevance. For example, if you sell a "blue wool beanie" and your product image has alt="Blue wool beanie with ribbed cuff", that text helps Google match the image to the phrase "blue wool beanie". It also helps the page be considered more relevant for that query. The technical name is "alt attribute", though most people call it "alt text". Avoid "alt tag" – it is not a tag. My rule of thumb: write a concise natural description of what the image shows, include the target keyword only if it fits naturally, and never force it. If the image is purely decorative, use alt="" so screen readers skip it. That last point is accessibility best practice and should be non-negotiable. For more examples of good alt text, see my [alt text examples](/alt-text-examples/). And if you want to dig into how images affect search performance, check the [image SEO](/image-seo/) page.

Alt text matters most when images carry information that text does not. For e-commerce product pages, each product image should have descriptive alt text because Google Image Search is a significant traffic source. I once ran a test and found that after adding descriptive alt text to 200 product images on a client's site, impressions from image search increased by 18% over six weeks. That number convinced me. For infographics and data visualisations, alt text is essential because screen readers cannot interpret a chart without a textual summary. Write a short sentence that captures the takeaway, not just "chart showing revenue growth". If you publish a recipe blog, the step-by-step photos benefit from alt text because users often search for "how to fold dumplings" and land on image results. A counter-argument I hear is that modern AI-powered screen readers can generate alt text automatically, so human-written text is less critical. I disagree. Automated descriptions are often generic or hallucinated. You lose control over the message. Another edge case: when your site has many decorative images, such as icons or spacers, never leave alt text blank – use alt="" explicitly. If you omit the alt attribute entirely, screen readers may read the file name. That is a poor user experience. For pages that are primarily image-heavy, like photographer portfolios, alt text is your only way to tell search engines what those images represent. Without it, the page has almost no textual content for ranking. Alt text is a core part of [onpage SEO](/onpage-seo/). And if you run a blog, pay extra attention to your images – read about [blog SEO](/blog-seo/) for more.

I used to stuff keywords into alt text. I thought "more keywords = more relevance". It did not work. It made descriptions read like "blue wool beanie warm winter hat beanie cap ski beanie" which is a nightmare for screen reader users and looks spammy to Google. I have since cleaned those up. I also left alt text blank on important images because I was rushing. That is a double loss: no accessibility and no SEO value. I assumed that if the image was decorative to me, it was decorative to everyone. But screen reader users may benefit from knowing there is an illustration or a photo, even if it is not content-critical. I now use alt="" only when the image is truly decorative, meaning it adds no information if removed. Another mistake: I wrote overly long alt text. I once wrote a 200-character description for a simple hero image. That is unnecessary and gets truncated. Keep it under 125 characters. I also used to treat alt text as a ranking manipulation lever. It is not. The SEO value comes from clarifying what the image is, not from forcing a phrase. A more recent error: I ignored alt text for SVGs and CSS background images because they are not <img> tags. SVGs inside <img> tags still need alt text, and decorative background images should be hidden from screen readers with aria-hidden="true". That is a nuance I missed for years. Good [SEO writing](/seo-writing/) means writing for both humans and machines. And if you need a refresher on the basics, revisit my [alt text](/alt-text/) guide.