Image SEO
Image SEO is the practice of optimising images on web pages to improve page performance and enable discovery through Google Image Search, using techniques like alt text, file names, compression, and structured data.
Reviewed by Alexander Yarovenko · Updated: 2026-09-22
What is Image SEO?
Image SEO encompasses the practices of optimising images on your web pages to improve page load speed, enable discovery via Google Images, and enhance overall page relevance signals. Images are often the largest page resources — optimising them is one of the highest-impact technical SEO improvements for most sites.
Image SEO Checklist
- Descriptive file names —
seo-audit-checklist.jpgnotIMG_4821.jpg - Alt text — describes the image for screen readers and provides keyword context to search engines
- Compress images — reduce file size without visible quality loss using tools like TinyPNG, Squoosh
- Use modern formats — WebP (30–50% smaller than JPEG) or AVIF (next-gen, even smaller)
- Set width and height attributes — prevents layout shift (CLS) as the page loads
- Lazy load below-the-fold images —
loading="lazy"attribute delays loading until needed - Preload LCP image — use
<link rel="preload" as="image">for the largest above-fold image - Use a CDN — serve images from servers close to the user
- Implement image sitemap — helps Google discover all your images
Alt Text Best Practices
- Be descriptive: describe what's actually in the image
- Include your target keyword if it naturally fits
- Keep it concise (under 125 characters)
- Don't start with "Image of..." or "Photo of..." (screen readers already announce it's an image)
- Leave alt="" (empty) for decorative images that convey no information
Image File Formats Guide
| Format | Best for | Notes |
|---|---|---|
| WebP | Photos and graphics | 30–50% smaller than JPEG; supported by all modern browsers |
| AVIF | Photos | Smallest file size; limited older browser support |
| SVG | Icons, logos, illustrations | Infinitely scalable; no quality loss |
| PNG | Screenshots with text, transparency needed | Lossless; larger files |
| JPEG | Photos (legacy) | Use WebP instead when possible |
Editorial decision
Publish useful images near relevant text with stable URLs, dimensions and efficient formats.
Validation
Check indexable image URL, alt, intrinsic size, loading and image sitemap need on representative live pages and record the result.