Image SEO is the practice of optimizing images on your website so search engines can understand, index, and rank them, including using descriptive file names, adding alt text, compressing file sizes, using modern formats like WebP, and implementing responsive images for faster loading. Properly optimized images can drive traffic from Google Images, improve page speed for better rankings, and enhance accessibility for users with screen readers. Image optimization is a critical part of both on-page SEO and technical SEO.
Images account for approximately 50% of the average webpage’s total size, making image optimization one of the biggest opportunities to improve page speed and Core Web Vitals. Beyond performance, image SEO helps your content appear in Google Images search results, which drives billions of searches monthly.
Key Takeaways: Image SEO
- Use descriptive file names: Name images with keywords before uploading (red-nike-running-shoes.jpg)
- Add alt text: Describe every image for accessibility and SEO
- Compress images: Reduce file size without sacrificing quality
- Use WebP format: Modern format with 25-35% smaller files than JPEG
- Implement lazy loading: Defer off-screen images to improve initial load time
12 Image SEO Best Practices
- Use descriptive file names – Include keywords, use hyphens between words
- Add alt text to every image – Describe what the image shows
- Compress images before uploading – Reduce file size by 50-80%
- Use WebP or AVIF formats – Modern formats with smaller file sizes
- Specify image dimensions – Set width and height to prevent layout shift
- Implement lazy loading – Load images as users scroll
- Use responsive images – Serve different sizes for different devices
- Add images to XML sitemap – Help Google discover your images
- Use a CDN for images – Serve images from servers closer to users
- Add captions when helpful – Captions are read more than body text
- Use unique, original images – Original images can rank better
- Add structured data – Enable rich results for products and recipes
Why Image SEO Matters
Google Images is the second-largest search engine after Google Search. Images appear in regular search results, image packs, and Google Discover. Optimized images load faster, improving user experience and Core Web Vitals scores. Alt text improves accessibility for visually impaired users. Every image is an opportunity to rank and drive traffic.
Egochi, America’s #1 digital marketing agency headquartered in New York City, optimizes images for every client website we build and audit. From our offices in NYC, Milwaukee, Madison, and Miami, we’ve seen firsthand how proper image optimization can dramatically improve page speed scores and search visibility.
What is image SEO?
Image SEO is the process of optimizing images to rank in search engines and improve website performance. It includes naming image files with descriptive keywords, adding alt text that describes the image, compressing files to reduce load time, using modern formats like WebP, and implementing technical optimizations like lazy loading and responsive images. Good image SEO helps images appear in Google Images results and improves overall page ranking.
How do I optimize images for SEO?
Optimize images for SEO by: (1) Naming files descriptively with keywords (blue-ceramic-coffee-mug.jpg), (2) Adding alt text that describes the image content, (3) Compressing images to reduce file size, (4) Using WebP or AVIF formats, (5) Setting explicit width and height attributes, (6) Enabling lazy loading for off-screen images, (7) Using responsive images with srcset, and (8) Including images in your XML sitemap. Tools like ShortPixel, TinyPNG, and Squoosh make optimization easy.
Does alt text help SEO?
Yes, alt text is one of the most important factors for image SEO. Alt text (alternative text) tells search engines what an image depicts since they can’t “see” images like humans do. Google uses alt text to understand image content and determine relevance for image search queries. Alt text also improves accessibility for screen reader users and displays when images fail to load. Write descriptive alt text that naturally includes relevant keywords.
Anatomy of an Optimized Image
src=“https://example.com/images/red-nike-air-max-90.webp”
alt=“Red Nike Air Max 90 running shoes on white background”
width=“800”
height=“600”
loading=“lazy”
/>
<!– File: red-nike-air-max-90.webp (45KB, compressed from 180KB) –>
Table of Contents
Image Formats for the Web
Choosing the right image format affects file size, quality, and browser compatibility:
Best Overall
25-35% smaller than JPEG with same quality. Supports transparency. 97% browser support.
RecommendedNext Generation
50% smaller than JPEG. Best compression. 92% browser support and growing.
ExcellentPhotos
Universal support. Good compression for photographs. No transparency.
StandardTransparency
Lossless quality. Supports transparency. Larger file sizes than JPEG/WebP.
Use Sparingly| Format | Best For | Transparency | Compression | Browser Support |
|---|---|---|---|---|
| WebP | All images (photos, graphics) | ✓ | Excellent | 97% |
| AVIF | Photos, detailed images | ✓ | Best | 92% |
| JPEG | Photos (fallback) | ✗ | Good | 100% |
| PNG | Graphics, screenshots, transparency | ✓ | Poor | 100% |
| SVG | Icons, logos, illustrations | ✓ | Scalable | 100% |
| GIF | Simple animations | ✓ | Poor | 100% |
Use the picture element with WebP as primary and JPEG as fallback for maximum compatibility. Modern browsers will load WebP; older browsers fall back to JPEG. Most CMS platforms and CDNs can automate this conversion.
Alt Text Best Practices
Alt text (alternative text) is one of the most important image SEO elements. It describes images for search engines and screen readers:
alt="image"alt="IMG_4532.jpg"alt="shoes running nike red buy best cheap"
alt="Red Nike Air Max 90 running shoes"alt="Woman jogging on beach at sunset"alt="Chocolate chip cookies cooling on wire rack"
Alt Text Guidelines:
- Be descriptive: Describe what the image actually shows
- Be concise: Keep alt text under 125 characters when possible
- Include keywords naturally: Don’t stuff keywords; write for humans first
- Skip “image of” or “picture of”: Screen readers already announce it’s an image
- Leave decorative images empty: Use alt=”” for purely decorative images
- Describe the function for linked images: If an image is a link, describe where it goes
Avoid Keyword Stuffing in Alt Text
Alt text should describe the image, not be a list of keywords. “Red shoes running shoes Nike shoes best running shoes cheap” is spam. “Red Nike Air Max 90 running shoes” is helpful. Google can detect keyword stuffing in alt text and may penalize your site.
Image File Name Optimization
Image file names are an often-overlooked SEO signal. Name images descriptively before uploading:
Use Descriptive Names
Change “IMG_4523.jpg” to “chocolate-chip-cookies-recipe.jpg”. Include what the image shows, not random numbers or codes.
Use Hyphens Between Words
Google reads hyphens as word separators. Use “blue-running-shoes.jpg” not “bluerunningshoes.jpg” or “blue_running_shoes.jpg”.
Include Relevant Keywords
If the image shows a red Nike Air Max shoe, name it “red-nike-air-max-90.jpg”. Be specific but natural.
Keep Names Concise
Aim for 3-5 words. Long file names are hard to manage and don’t provide extra SEO value. Focus on the most descriptive terms.
Use Lowercase Letters
Stick to lowercase for consistency and to avoid potential server issues. “Product-Image.jpg” and “product-image.jpg” may be treated as different files.
Avoid Special Characters
Don’t use spaces, underscores, or special characters in file names. Stick to letters, numbers, and hyphens only.
Image Compression and Performance
Large images are the #1 cause of slow websites. Compression reduces file size while maintaining visual quality:
⚡ Image Speed Optimization
Compress Files
Reduce JPEG quality to 80-85% for 50%+ savings
Right Size
Don’t upload 4000px images for 800px displays
Modern Formats
WebP/AVIF are 25-50% smaller than JPEG
Use a CDN
Serve images from servers near users
Compression Tips:
- Target 100KB or less for most web images
- Hero images can be 150-250KB if needed for quality
- Thumbnails should be under 30KB
- Use lossy compression for photos (JPEG, WebP)
- Use lossless for graphics with text or sharp edges
Image Optimization Tools
TinyPNG
Simple compression for PNG/JPEG
FreemiumShortPixel
WordPress plugin + API
FreemiumSquoosh
Google’s free online tool
FreeImageOptim
Mac desktop app
FreeCloudflare
CDN with auto-optimization
FreemiumImagify
WordPress optimization
FreemiumSmush
Popular WordPress plugin
FreemiumEWWW
WordPress + server tools
PaidAutomate image optimization. Use a WordPress plugin like ShortPixel or Imagify to compress images on upload. Or use a CDN like Cloudflare or imgix that optimizes and serves images automatically in the best format for each browser.
Technical Image SEO
Beyond basic optimization, these technical elements improve image SEO:
Lazy Loading
Add loading=”lazy” to images below the fold. This defers loading until users scroll near them, improving initial page load. Native lazy loading has 95%+ browser support.
Explicit Dimensions
Always specify width and height attributes. This prevents Cumulative Layout Shift (CLS) by reserving space before the image loads. Critical for Core Web Vitals.
Responsive Images
Use srcset and sizes attributes to serve appropriately sized images for each device. Don’t send 2000px images to mobile phones with 400px screens.
Image Sitemaps
Include images in your XML sitemap or create a dedicated image sitemap. This helps Google discover images, especially those loaded via JavaScript.
Structured Data
Add schema markup for products, recipes, and articles that include images. This enables rich results with image thumbnails in search.
Preload Critical Images
Use rel=”preload” for LCP images (usually hero images). This tells browsers to fetch these images early, improving Largest Contentful Paint scores.
Common Image SEO Mistakes
Missing Alt Text
Every content image needs alt text. Empty alt text means lost SEO value and accessibility issues.
Uploading Uncompressed Images
Camera photos are often 2-5MB. Compress to under 200KB for web use. Huge images kill page speed.
Using Generic File Names
“IMG_4523.jpg” tells search engines nothing. Rename with descriptive, keyword-rich names.
Wrong Dimensions
Uploading 4000px images when you only display 800px wastes bandwidth and slows pages.
Keyword Stuffing Alt Text
“shoes running shoes nike shoes best running shoes” is spam. Write natural descriptions.
No Lazy Loading
Loading all images immediately slows initial page load. Use lazy loading for images below the fold.
Missing Width/Height
Without dimensions, images cause layout shift as they load. This hurts CLS scores.
Using Only JPEG/PNG
WebP offers 25-35% smaller files with same quality. Most browsers support it now.
Image SEO Checklist
- ✓ All images have descriptive, hyphenated file names
- ✓ Every content image has meaningful alt text
- ✓ Images are compressed (target under 100KB for most)
- ✓ Using WebP format with JPEG fallback
- ✓ Images have explicit width and height attributes
- ✓ Lazy loading enabled for below-the-fold images
- ✓ Responsive images using srcset for different screen sizes
- ✓ Hero/LCP images are preloaded
- ✓ Images included in XML sitemap
- ✓ Using a CDN for image delivery
- ✓ Product and recipe images have structured data
- ✓ Core Web Vitals passing (LCP under 2.5s)
People Also Ask About Image SEO
How many keywords should be in alt text?
Focus on describing the image naturally, not keyword count. If a relevant keyword fits naturally in the description, include it. But don’t force keywords into alt text. “Red Nike running shoes on white background” is better than stuffing multiple keyword variations. One well-placed keyword in natural context is enough.
Should I use JPEG or PNG for SEO?
Use WebP as your primary format, with JPEG or PNG as fallbacks. For photographs, JPEG (or WebP) offers good compression. For graphics with transparency, text, or sharp edges, PNG (or WebP) maintains quality. WebP handles both use cases with smaller file sizes. Format choice affects page speed, which impacts SEO.
Does image file size affect SEO?
Yes, file size significantly affects SEO through page speed. Large images slow page loading, hurting Core Web Vitals scores and user experience. Google uses page speed as a ranking factor. Slow-loading images can also prevent Googlebot from fully crawling your pages within its crawl budget.
Should decorative images have alt text?
Decorative images should have empty alt text (alt=””), not no alt attribute. The empty alt tells screen readers to skip the image. Omitting the alt attribute entirely causes screen readers to read the file name, which is confusing. Reserve descriptive alt text for images that convey meaningful content.
Do captions help image SEO?
Yes, captions can help image SEO. Studies show people read captions more than body text. Captions provide context that helps users and search engines understand images. While not as important as alt text or file names, captions add keyword context and improve user engagement with images.
Image Optimization Services from Egochi
Egochi, America’s #1 digital marketing agency headquartered in New York City, optimizes images as part of our technical SEO services.
Performance Audits: Our SEO audits include detailed image analysis identifying uncompressed images, missing alt text, wrong formats, and other issues hurting your Core Web Vitals and rankings.
Speed Optimization: We implement automated image optimization workflows including compression, WebP conversion, lazy loading, and CDN delivery to dramatically improve page speed scores.
Alt Text Strategy: We develop alt text guidelines and can audit existing images to ensure every image on your site contributes to SEO while maintaining accessibility.
Proven Results: From our offices in NYC, Milwaukee, Madison, and Miami, we’ve helped clients reduce image sizes by 60-80% while improving visual quality, resulting in faster pages and better rankings.
Need Image Optimization Help?
Get a free image audit from Egochi. We’ll analyze your images and show you exactly what to optimize.
Get a Free Image AuditOr call (888) 644-7795
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