Glossary
Image SEO
The practice of optimizing images for search engines through proper file formatting, compression, descriptive filenames, alt text, and structured data to improve visibility in image search and enhance webpage performance.
Image SEO encompasses techniques that make visual content more accessible to search engines while improving user experience. Since search engines cannot "see" images, they rely on contextual signals to understand and properly index visual content. Proper image optimization begins with selecting the right file format (typically JPEG for photographs, PNG for graphics with transparency, or WebP for optimal compression) and compressing files to minimize page load time without sacrificing quality. Descriptive filenames (landscape-photography-yosemite-valley.jpg rather than IMG12345.jpg) and comprehensive alt text that describes the image content for visually impaired users provide crucial context for search engines. Additionally, implementing responsive images that adapt to different screen sizes, adding captions where appropriate, and using image sitemaps help search engines discover and properly index your visual content. Advanced image SEO techniques include adding structured data markup to identify specific image types (like products, recipes, or logos), ensuring proper color contrast for accessibility, creating unique images rather than using stock photography, and optimizing for visual search features like Google Lens. With nearly one-third of all searches occurring on Google Images, comprehensive image optimization represents a significant opportunity to capture additional traffic from visual search.