Image SEO
Image SEO is the practice of making images easy for search engines to discover, understand, and display while improving page speed and accessibility.
Key takeaways
- Descriptive filenames and alt text help Google understand image context.
- Compression and modern formats (WebP) improve page speed and Core Web Vitals.
- Width/height attributes prevent layout shifts (CLS).
- Image sitemaps help Google discover images that are hard to find.
- Avoid keyword stuffing in alt text and oversized images.
Optimized images help your content appear in Google Images, support page relevance, and improve Core Web Vitals.
Example: Optimizing a Product Image
You have a photo of red running shoes for a blog post.
Before (poor SEO):
- Filename:
IMG_4521.jpg - Alt text:
shoes - Size: 5 MB, 4000×3000 px
- Format: JPEG
After (optimized):
- Filename:
red-running-shoes-women.jpg - Alt text:
Woman wearing red running shoes on a forest trail - Size: 120 KB, 1200×900 px
- Format: WebP
- Added
width="1200" height="900"to the<img>tag - Included in an image sitemap
Result: Faster page load, better accessibility, and higher chance of appearing in Google Images.
Quick-Start: 5 Steps to Optimize Any Image
- Rename the file – Use descriptive, hyphenated words (e.g.,
blue-widget.jpg). - Write alt text – Describe the image accurately for accessibility; include a keyword only if natural.
- Compress and resize – Use a tool like Squoosh to reduce file size and match display dimensions.
- Choose a modern format – Convert to WebP for best compression/quality balance.
- Add width and height – Set
widthandheightattributes in the<img>tag to prevent layout shifts.
How to Judge If Your Images Are Optimized
- File size – Each image should be under 200 KB (ideally under 100 KB for thumbnails).
- Dimensions – Match the display size; don't serve a 4000 px image for a 300 px thumbnail.
- Format – Use WebP or AVIF for photos; SVG for icons and logos.
- Alt text – Every meaningful image has alt text; decorative images use
alt="". - Layout shift – Check that width/height attributes are set (use Chrome DevTools > Performance).
- Crawlability – Images should not be blocked by
robots.txtor hidden in CSS backgrounds.
Common Image SEO Mistakes
- Generic filenames –
IMG_1234.jpgtells Google nothing. - Keyword-stuffed alt text –
red shoes buy cheap red shoes onlinehurts accessibility and may be seen as spam. - Oversized images – Uploading a 5 MB photo and scaling it with CSS wastes bandwidth and slows the page.
- Missing dimensions – Without
widthandheight, the page can jump as images load, hurting CLS. - Blocking images – Using CSS
background-imagefor important content or blocking image paths inrobots.txthides them from search.
Next step
FAQ
What is image SEO?
Image SEO is the practice of optimizing images so search engines can discover, understand, and rank them, improving visibility in Google Images and page performance.
How do I write good alt text?
Describe the image accurately and concisely for accessibility; avoid keyword stuffing. Include relevant keywords naturally if they fit the context.
What image format is best for SEO?
WebP is recommended for web use due to superior compression and quality. JPEG and PNG remain acceptable; SVG is best for vector graphics.
Related topics
Sources
- Google Search Central: Image SEO Best Practices — Primary source for discovery, indexing, responsive images, sitemaps, formats, and image-page optimization.
- Yoast: Image SEO — Widely cited SEO reference with practical guidance on filenames, dimensions, alt text, structured data, and sitemaps.
- Search Engine Journal: Image Optimization Tips — Useful secondary SEO reference covering alt text, compression, responsive images, lazy loading, and crawlability.
Reviewed by Lucía Marín, Founding editor.