Technical SEO

Alt Text SEO

Alt text (alternative text) is an HTML attribute on image elements that describes the content of an image in words. For SEO, alt text is a direct keyword relevance signal that helps Google understand image content and contributes to page-level keyword context — while also serving as the primary accessibility mechanism for visually impaired users.

Quick Answer

Alt text (alternative text) is an HTML attribute on image elements that describes the content of an image in words. For SEO, alt text is a direct keyword relevance signal that helps Google understand image content and contributes to page-level keyword context — while also serving as the primary accessibility mechanism for visually impaired users.

  • Describe the image, not the keyword — alt text should accurately describe what's in the image; keyword inclusion is secondary to accuracy and risks spam penalties if forced
  • Empty alt for decorative images — images that are purely decorative (dividers, background patterns) should use alt="" to prevent screen readers from announcing them unnecessarily
  • Character limit — keep alt text under 125 characters; screen readers truncate at this length and longer alt text often indicates over-optimization

Key Takeaways

  • Describe the image, not the keyword — alt text should accurately describe what's in the image; keyword inclusion is secondary to accuracy and risks spam penalties if forced
  • Empty alt for decorative images — images that are purely decorative (dividers, background patterns) should use alt="" to prevent screen readers from announcing them unnecessarily
  • Character limit — keep alt text under 125 characters; screen readers truncate at this length and longer alt text often indicates over-optimization

How Alt Text SEO Works

Alt text is written into the HTML img tag as the alt="" attribute: <img src="product.jpg" alt="red leather office chair with lumbar support">. When a browser cannot display an image (slow connection, image load failure), the alt text is displayed in its place. For screen readers used by visually impaired users, alt text is read aloud as the description of the image. For Google's crawlers, which cannot "see" images, alt text is the primary signal describing what the image depicts. This makes alt text simultaneously an accessibility requirement (WCAG 2.1 Success Criterion 1.1.1) and an SEO relevance signal.

Why Alt Text SEO Matters for B2B Marketing

From an SEO perspective, alt text contributes to keyword relevance at the page level. A page about "industrial conveyor belt systems" with images using alt text like "industrial conveyor belt system for automotive manufacturing" sends consistent, reinforcing topical signals across both the text content and the image metadata. Alt text also directly determines whether images rank in Google Image Search for relevant queries — images without descriptive alt text rely entirely on surrounding context for image search ranking, and they consistently underperform images with specific, descriptive alt text.

Alt Text SEO: Best Practices & Strategic Application

Best practices for SEO-optimized alt text: (1) describe the image accurately and specifically — "woman using laptop in modern office" is better than "office photo," (2) include the primary keyword naturally if it genuinely reflects the image content — don't force it, (3) keep alt text concise — 50–125 characters is the practical range, (4) avoid starting with "image of" or "photo of" — Google's crawlers already know it's an image, (5) use empty alt attributes (alt="") for purely decorative images that add no informational value, to prevent screen readers from reading irrelevant descriptions.

Agency Perspective: Alt Text SEO in Practice

Alt text audits are a standard component of MV3's technical SEO reviews. We consistently find that 30–50% of images on client websites have missing, generic, or keyword-stuffed alt text. Missing alt text is the most common WCAG violation on commercial websites and carries both SEO and legal risk (ADA accessibility lawsuits are increasingly common, particularly for US businesses). A systematic alt text audit and rewrite typically takes 4–8 hours for sites under 500 pages and produces measurable improvements in image search impressions within 4–8 weeks.

Frequently Asked Questions: Alt Text SEO

Related Terms

Image SEOOrganization Schema

Put Alt Text SEO Into Practice

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