Image SEO Checklist: 15 Ways to Optimize Images for Google

Images can bring traffic from Google Images, improve engagement, and make content easier to understand. But unoptimized images can also slow down pages and hurt Core Web Vitals.

Use this image SEO checklist before publishing important pages.

1. Use Descriptive File Names

Rename files before uploading. A file like blue-running-shoes.webp is more helpful than IMG_4839.webp.

Good filenames describe the image in plain words:

• webp-quality-settings-chart.webp
• compress-image-before-after.webp
• png-vs-webp-file-size.webp

2. Add Helpful Alt Text

Alt text should describe the image for people who cannot see it. It also gives search engines context.

Good alt text is specific but not spammy. Avoid stuffing keywords into every image.

3. Compress Images Before Uploading

Large images slow down pages. Use Compress Image before uploading images to your website.

For most web content, WebP at 75–85% quality is a strong starting point.

4. Convert JPG and PNG to WebP

WebP is widely supported and often much smaller than JPG or PNG. Use:

• JPG to WebP for photos
• PNG to WebP for graphics and screenshots
• Image to WebP for mixed formats

5. Resize Images to the Correct Dimensions

Do not upload a 4000px image if it displays at 900px. Resize images to match the largest display size needed by your layout.

6. Use Responsive Images

Use srcset and sizes so browsers can download smaller images on smaller screens. This is especially important for mobile SEO.

7. Lazy Load Below-the-Fold Images

Lazy loading delays off-screen images until users scroll near them. This can improve initial load speed. Learn more in Lazy Loading Images.

Do not lazy load the main hero image if it is the Largest Contentful Paint element.

8. Set Width and Height

Define image dimensions to reduce layout shift. This helps Cumulative Layout Shift (CLS), one of the Core Web Vitals metrics.

9. Use Captions When Helpful

Captions are often read more than body text. Use them for charts, comparisons, product details, and educational images.

10. Create an Image Sitemap When Needed

Large image-heavy sites can benefit from image sitemap data. This helps Google discover important images.

11. Avoid Text-Only Images

If important text is inside an image, search engines and screen readers may not understand it well. Use real HTML text whenever possible.

12. Use Unique Images Where Possible

Original images can help content stand out. Stock images are fine when useful, but unique screenshots, charts, and examples often perform better.

13. Optimize Open Graph Images

Social sharing images should be clear, branded, and lightweight. Use compressed WebP or optimized JPG depending on platform support.

14. Check Core Web Vitals

Use PageSpeed Insights or Lighthouse to test image impact on Largest Contentful Paint and total page weight. Read WebP and Core Web Vitals for details.

15. Keep a Repeatable Workflow

A simple image SEO workflow:

1. Rename the image descriptively.
2. Resize to the right dimensions.
3. Convert or compress to WebP.
4. Add alt text.
5. Set width and height.
6. Lazy load below-fold images.
7. Test page speed.

Conclusion

Image SEO is not just alt text. It includes file size, format, dimensions, accessibility, page speed, and context. Start by converting and compressing your images with ImageToWebP, then follow this checklist every time you publish.