How to optimize images for SEO in 2026

Complete guide to optimizing images and improving Google rankings: size, format, alt text, lazy loading and more.

Why do images affect SEO?

Poorly optimized images are one of the main causes of slow websites, and speed is a direct Google ranking factor since 2021 (Core Web Vitals). Additionally, well-optimized images appear in Google Images, generating additional traffic.

The 6 pillars of image optimization for SEO

1. Correct format

Use WebP for web images whenever possible — it's 25-35% smaller than JPG. Use JPG for photos and PNG only when you need transparency.

2. Ideal file size

Images above 200KB negatively impact Core Web Vitals. Google PageSpeed recommends each image be under 100KB whenever possible.

3. Correct dimensions

Never load a 2000px image to display at 400px. Resize the image to the exact dimensions that will be displayed on the site before uploading.

4. Descriptive alt text

The alt attribute describes the image to Google and visually impaired users. Write short, descriptive text with the main keyword when natural.

5. File name

Rename files with hyphen-separated keywords before uploading: compress-image-online.jpg instead of IMG_20240315.jpg.

6. Lazy Loading

Add loading="lazy" to all below-the-fold images. This defers loading of images the user can't see yet, improving LCP and PageSpeed scores.

SEO optimization checklist

• ✅ WebP or JPG format (not PNG for photos)
• ✅ File under 200KB (ideally under 100KB)
• ✅ Dimensions equal to display size on site
• ✅ Descriptive alt text with keyword
• ✅ Keyword-rich file name
• ✅ loading="lazy" for below-fold images
• ✅ width and height defined in HTML (prevents CLS)