Image Optimization for SEO: A Practical Guide

Why Image Optimization Matters for SEO

Images often account for 50-80% of a webpage's total size. Google has confirmed that page speed is a ranking factor, and Core Web Vitals (including Largest Contentful Paint) directly impact search rankings.

Key Image SEO Factors

1. File Size and Format

Choose the right format for each image type:

• Photos: WebP (or JPEG fallback) at 75-85% quality

• Graphics/logos: SVG (or PNG if SVG isn't possible)

• Icons: SVG or optimized PNG

2. Image Dimensions

Never serve images larger than their display size. If an image displays at 800px wide, don't serve a 3000px original.

Responsive images tip: Use the srcset attribute to serve different sizes:

``html

`

3. Alt Text

Write descriptive, relevant alt text for every image. This helps:

• Accessibility — Screen readers use alt text

• SEO — Search engines understand image content

• Image search — Appear in Google Image results

4. File Names

Use descriptive, keyword-rich file names:

• ❌ IMG_2847.jpg

• ✅ blue-running-shoes-nike.jpg

5. Lazy Loading

Add loading="lazy" to images below the fold:

`html `

6. Width and Height Attributes

Always specify dimensions to prevent Cumulative Layout Shift (CLS):

`html ``

Quick Checklist

• [ ] Use WebP format where possible

• [ ] Compress all images (75-85% quality for photos)

• [ ] Resize to actual display dimensions

• [ ] Write descriptive alt text

• [ ] Use descriptive file names

• [ ] Add lazy loading for below-fold images

• [ ] Specify width and height attributes

• [ ] Use a CDN for image delivery

• [ ] Implement responsive images with srcset

Tools for Image Optimization

• FormatPic — Free browser-based format conversion and compression

• Lighthouse — Google's built-in performance audit tool

• PageSpeed Insights — Google's web performance tool