Technical SEO
Image Optimization
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What is Image Optimization?
Image optimization encompasses a set of techniques for reducing image file sizes and improving their discoverability without sacrificing visual quality. This includes choosing the right file format (WebP or AVIF over JPEG/PNG for photos), compressing images to appropriate quality levels, serving responsive images via srcset attributes, specifying explicit width and height to prevent layout shifts, and writing descriptive alt text.
From an SEO perspective, optimized images load faster (improving LCP and overall page speed), contribute to lower Cumulative Layout Shift scores, and are more likely to appear in Google Image Search when properly described with alt attributes and surrounding contextual text. Large, unoptimized images are one of the most common causes of poor Core Web Vitals scores on content-rich pages.
Why it matters for SEO
Images are frequently the heaviest assets on a page and the primary driver of poor LCP scores. Proper image optimization improves Core Web Vitals across LCP, CLS, and overall load speed — all factors Google uses as ranking signals — while also opening an additional traffic channel through image search.
Example
A travel blog uploads a 4,000-pixel-wide 5 MB JPEG as its article header, displayed at 1,200 pixels. Optimising it means resizing to the displayed dimensions, converting to WebP or AVIF, offering smaller versions through srcset for phones, adding width and height attributes to reserve space and prevent layout shift, and writing alt text such as "Sunrise over the rice terraces in Banaue, Philippines" rather than "IMG_2041".
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