HTML attribute describing an image's content for accessibility and search engines, important for image SEO.
Alt text is an HTML attribute that provides a textual description of an image's content, serving both accessibility and SEO purposes. When an image fails to load or when screen readers encounter it, the alt text displays or is read aloud instead, making web content accessible to visually impaired users while giving search engines context about the image's relevance to the surrounding content.
This seemingly simple attribute has become increasingly important as search engines evolve their understanding of multimedia content. Google's algorithms use alt text as a primary signal for image search results and as supporting context for overall page relevance, making it a crucial component of comprehensive SEO strategy.
Why It Matters for AI SEO
AI-powered search engines rely heavily on textual context to understand visual content, making alt text more valuable than ever. Google's Vision AI and similar technologies can recognize objects in images, but they still depend on alt text to understand the specific context and intent behind an image's placement on a page. When AI systems process your content for features like AI Overviews or answer generation, well-crafted alt text helps them connect visual elements to textual content. Modern AI also considers alt text when evaluating content quality and topical authority. Pages with comprehensive, contextually relevant alt text signal to AI systems that the content creator has invested in providing a complete user experience, potentially boosting overall content scores and ranking potential.
How It Works
Effective alt text should describe the image's content while connecting it to the page's topic. For an article about sustainable gardening featuring an image of composting, the alt text might read "hands turning compost pile with kitchen scraps and dry leaves" rather than generic text like "composting." This approach provides both accessibility value and SEO context. Tools like Screaming Frog and Sitebulb can audit your site for missing alt text, while platforms like Ahrefs and SEMrush help identify opportunities where improved image optimization could drive additional organic traffic. When implementing alt text at scale, focus on images above the fold first, then product images, and finally decorative elements that add meaningful context.
Common Mistakes
The most frequent error is keyword stuffing alt text with target phrases that don't naturally describe the image. Search engines recognize this manipulation and may devalue overly optimized alt attributes. Another common mistake is writing alt text that duplicates the image caption or surrounding text verbatim—alt text should complement, not repeat, visible content. Finally, many sites either skip alt text entirely for decorative images (when alt="" would be appropriate) or provide generic descriptions like "image" or "photo" that offer no value to users or search engines.