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Image SEO Checklist: File Names, Alt Text & Optimization
Images can drive significant traffic from Google Image Search. Properly optimized images also improve page load times, which affects your Core Web Vitals and overall SEO. This checklist covers everything you need to optimize images for search engines.
Compress Images for Better SEO
Page speed is a ranking factor. Compress your images to improve load times without sacrificing quality.
Compress ImagesThe Complete Image SEO Checklist
Use this checklist for every image you add to your website. Each item contributes to better search visibility and user experience.
Quick Reference Checklist
- File name - Descriptive, keyword-rich, hyphens between words
- Alt text - Describes image content, includes keyword naturally
- File size - Compressed to under 100KB when possible
- Dimensions - Resized to actual display size
- Format - WebP with fallback, or optimized JPEG/PNG
- Lazy loading - Enabled for below-the-fold images
- Responsive images - srcset for different screen sizes
1. File Naming Best Practices
Google uses file names to understand image content. A descriptive file name is one of the simplest yet most overlooked SEO techniques.
- IMG_4582.jpg
- DSC00123.png
- photo1.jpeg
- screenshot_2026-01-23.png
- final_final_v2.jpg
- red-running-shoes-nike.jpg
- homemade-chocolate-cake.png
- tokyo-skyline-night.jpeg
- wooden-desk-organizer.png
- blue-ceramic-coffee-mug.jpg
File naming rules:
- Use lowercase letters only
- Separate words with hyphens (not underscores)
- Keep it concise (3-5 words)
- Include the primary keyword
- Describe what's actually in the image
- Avoid generic words like "image" or "photo"
2. Alt Text Optimization
Alt text is the most important image SEO element. It tells search engines (and screen readers) what the image shows.
Google's Guidance on Alt Text
"When writing alt text, focus on creating useful, information-rich content that uses keywords appropriately and is in context of the content of the page."
| Quality | Example | Why |
|---|---|---|
| Bad | alt="image" | No useful information |
| Bad | alt="shoes shoes nike running shoes buy now" | Keyword stuffing |
| OK | alt="running shoes" | Too generic |
| Good | alt="Nike Air Max red running shoes side view" | Descriptive, specific, includes keyword |
Alt text best practices:
- Keep it under 125 characters
- Describe the image content accurately
- Include target keyword naturally (don't force it)
- Don't start with "Image of" or "Picture of"
- For decorative images, use alt="" (empty)
- Be specific about what's shown
3. Image Compression
Page speed is a confirmed Google ranking factor. Large images are often the biggest cause of slow-loading pages.
Use our free image compressor to reduce file sizes while maintaining visual quality.
4. Image Dimensions
Serving images at larger dimensions than needed wastes bandwidth and slows page loads. Always resize images to their actual display size.
Common Mistake
Uploading a 4000x3000 pixel image and letting CSS scale it down to 800x600. This forces browsers to download a 5MB file when a 200KB file would suffice.
Use the Pictey Image Resizer to resize images to your needed dimensions.
5. Image Format Selection
Choosing the right format significantly impacts file size and quality. Here's when to use each:
| Format | Best For | Compression |
|---|---|---|
| WebP | All web images (if supported) | 25-35% smaller than JPEG |
| JPEG | Photographs, complex images | Lossy, good compression |
| PNG | Graphics, logos, transparency | Lossless, larger files |
| AVIF | Modern browsers (best compression) | 50% smaller than JPEG |
Learn more in our guide to image formats.
6. Lazy Loading
Lazy loading delays loading images until they're about to enter the viewport. This improves initial page load time.
HTML:
<img src="image.jpg" alt="Description" loading="lazy">Lazy loading rules:
- Don't lazy load above-the-fold images (LCP element)
- Do lazy load images below the fold
- Native browser lazy loading is now widely supported
7. Responsive Images
Serve different image sizes for different screen sizes using srcset:
HTML:
<img
srcset="image-400.jpg 400w,
image-800.jpg 800w,
image-1200.jpg 1200w"
sizes="(max-width: 600px) 400px,
(max-width: 1200px) 800px,
1200px"
src="image-800.jpg"
alt="Description"
>8. Structured Data for Images
Add schema markup to help Google understand your images:
Include image property in product markup for rich results in Google Shopping.
Add image property to article markup for better display in search results.
9. Image Sitemap
Help Google discover your images by including them in your sitemap:
XML Sitemap:
<url>
<loc>https://example.com/page</loc>
<image:image>
<image:loc>https://example.com/image.jpg</image:loc>
<image:title>Image title</image:title>
</image:image>
</url>10. Core Web Vitals Impact
Images affect two key Core Web Vitals metrics:
If your hero image is the largest element, optimize it for fast loading. Target under 2.5 seconds.
Always specify width and height attributes to prevent layout shifts as images load.
Learn more about image performance in our PageSpeed optimization guide.
Conclusion
Image SEO is a combination of technical optimization and content best practices. By following this checklist, you improve both your search visibility and user experience. Start with the basics - file names, alt text, and compression - then work your way through the more technical items.
Remember: every image on your site is an opportunity to rank in Google Image Search and drive traffic to your pages.
Optimize Your Images for SEO
Compress, resize, and convert images to boost your page speed and search rankings.