How to Do Image SEO

TL;DR

Image SEO optimizes your images to rank in Google Images and enhance your web pages for regular search. Key factors include: descriptive file names before uploading, alt text that describes the image for accessibility and search, proper file format and compression for fast loading, image dimensions that match display size, and image sitemaps for large image libraries. Google Images drives significant traffic for visual industries (e-commerce, travel, recipes, design), and images with good SEO can surface in regular search results through image packs. The most overlooked factor: alt text should describe what’s in the image, not stuff keywords.

Do This Today (3 Quick Checks)

Audit your alt text: Check 10 random images on your site. Do they have alt text? Does the alt text describe the image, or is it missing/generic? Missing alt text = missed SEO and accessibility.

Check image file sizes: Use PageSpeed Insights on a key page. Are images flagged for size? Large, uncompressed images hurt page speed and rankings.

Review file names: Look at your image URLs. Are they descriptive (blue-running-shoes.jpg) or generic (IMG4532.jpg)? File names are a ranking signal.

Responsive Images with Srcset

The problem: Serving a 2000px image to a phone screen wastes bandwidth and slows loading.

The solution: Use srcset to serve different image sizes based on device.

<img 
  src="product-800.jpg" 
  srcset="product-400.jpg 400w,
          product-800.jpg 800w,
          product-1200.jpg 1200w,
          product-1600.jpg 1600w"
  sizes="(max-width: 600px) 400px,
         (max-width: 1000px) 800px,
         1200px"
  alt="Blue leather office chair with adjustable armrests"
>

How it works:

Browser checks device width and pixel density
Chooses appropriate image size from srcset
Downloads only the size needed

Generate responsive images:

WordPress: Built into media library (generates multiple sizes)
Cloudinary/Imgix: Automatic responsive image generation
Manual: Create 4-5 sizes (400, 800, 1200, 1600, 2000px wide)

Common sizes to generate:

Size	Use Case
400px	Mobile thumbnails
800px	Mobile full-width
1200px	Tablet, small desktop
1600px	Desktop
2000px	Large desktop, retina

Image CDN Benefits

What is an image CDN?
A content delivery network optimized for images that automatically:

Serves images from servers closest to user
Compresses images
Converts to modern formats (WebP, AVIF)
Resizes based on device
Caches for faster repeat visits

Popular image CDNs:

Service	Free Tier	Best For
<strong>Cloudflare</strong>	Yes (with their CDN)	Sites already on Cloudflare
<strong>Cloudinary</strong>	25 credits/month	Dynamic image manipulation
<strong>Imgix</strong>	No free tier	Enterprise, heavy image sites
<strong>Bunny.net</strong>	Very cheap	Budget-conscious sites
<strong>ShortPixel Adaptive</strong>	Limited free	WordPress sites

Benefits for SEO:

Faster page speed (Core Web Vitals improvement)
Automatic WebP/AVIF serving
Reduced server load
Better mobile experience

Implementation:
Most image CDNs work by changing your image URLs:

Before: https://yoursite.com/images/product.jpg
After:  https://cdn.yoursite.com/images/product.jpg?w=800&format=webp

ImageObject Schema Markup

Help Google understand your images with structured data:

{
  "@context": "https://schema.org",
  "@type": "ImageObject",
  "contentUrl": "https://example.com/images/blue-leather-chair.jpg",
  "name": "Blue Leather Office Chair",
  "description": "Ergonomic blue leather office chair with lumbar support and adjustable armrests",
  "width": "1200",
  "height": "800",
  "author": {
    "@type": "Person",
    "name": "John Smith"
  },
  "copyrightHolder": {
    "@type": "Organization",
    "name": "Example Furniture Co"
  },
  "license": "https://example.com/image-license"
}

When to use ImageObject:

Original photography you want attributed
Images you want appearing in Google Images with credit
Stock photography with licensing requirements
Product images where you want rich results

Combine with other schema:

Product schema: Include images in product markup
Article schema: Include images in article markup
Recipe schema: Include images for recipe rich results

Visual Search and Pinterest SEO

Google Lens optimization:

High-quality, clear images
Product on plain background performs better
Multiple angles of same product
Descriptive file names and alt text
Product schema with image property

Pinterest SEO (for visual industries):

Vertical images (2:3 ratio) perform best
Text overlay on images increases engagement
Descriptive pin titles (like SEO titles)
Keyword-rich pin descriptions
Link to relevant landing page
Use Rich Pins (Product, Recipe, Article)

Industries that benefit most from visual search:

Fashion and apparel
Home decor and furniture
Food and recipes
Travel and destinations
Art and design
Beauty and cosmetics

Image SEO Ranking Factors

Factor	Impact	How to Optimize
<strong>Alt text</strong>	High	Describe image content accurately, naturally include relevant keywords
<strong>File name</strong>	Medium	Descriptive name before upload (red-velvet-cake.jpg not IMG001.jpg)
<strong>Surrounding content</strong>	High	Image should be contextually relevant to page content
<strong>Page authority</strong>	High	Images on authoritative pages rank better
<strong>Image quality</strong>	Medium	High-resolution, clear images preferred
<strong>File size/load speed</strong>	Medium	Compressed files, proper dimensions
<strong>Image sitemap</strong>	Medium	Helps discovery for large image libraries
<strong>Structured data</strong>	Medium	Product, Recipe schema can surface images in rich results

Image File Best Practices

File naming:

Good: red-leather-office-chair.jpg
Bad: IMG_4829.jpg
Bad: chair.jpg
Bad: red-leather-office-chair-best-ergonomic-office-chair-for-back-pain.jpg (keyword stuffing)

File format selection:

Format	Best For	Pros	Cons
<strong>WebP</strong>	Most web images	Smallest file size, modern	Older browser support
<strong>JPEG</strong>	Photos, complex images	Wide support, good compression	Lossy, no transparency
<strong>PNG</strong>	Graphics with transparency	Lossless, transparency	Large file sizes
<strong>SVG</strong>	Icons, logos, illustrations	Scalable, tiny size	Not for photos
<strong>AVIF</strong>	Cutting-edge quality	Best compression	Limited browser support

Recommended approach: Use WebP with JPEG fallback for photos. Use SVG for icons/logos. Use PNG only when transparency is required.

Compression targets:

Hero images: Under 200KB ideally
Content images: Under 100KB
Thumbnails: Under 30KB

The Conversation

Leo, runs an outdoor furniture e-commerce site, 500 products with 5-10 images each, images currently unoptimized (large files, generic names), noticing slow page speed and minimal Google Images traffic, basic technical knowledge: We have about 3,000 product images on our site. Our page speed scores are terrible, and we’re getting almost no traffic from Google Images. When I search “outdoor dining table” on Google Images, competitors show up but we don’t, even though we have great product photography. What are we doing wrong?

SDC SEO Brain: With 3,000 images and page speed issues, you likely have both optimization problems (images too large, not compressed) and SEO problems (poor file names, missing alt text, no image sitemap). Let’s diagnose each. First, run one of your product pages through PageSpeed Insights. What’s the Largest Contentful Paint score, and does it flag images as an issue?

Leo: LCP is 4.8 seconds on mobile. It says “Properly size images” and “Serve images in next-gen formats” with a lot of items flagged.

SDC SEO Brain: 4.8 seconds LCP is poor (should be under 2.5s), and images are clearly the cause. Your images are probably: too large in file size, possibly larger dimensions than display size, and likely in JPEG/PNG format rather than WebP. Let’s check file sizes. Pick a typical product image and tell me the file size.

Leo: One product image is 2.4MB.

SDC SEO Brain: That’s massive. A well-optimized product image should be 50-150KB, not 2.4MB. Your images are roughly 20x larger than they should be. This is your page speed problem and contributes to your Google Images problem (Google prefers fast-loading pages).

Leo: How do I compress them without losing quality?

SDC SEO Brain: Several approaches:

For future uploads: Use tools like TinyPNG, Squoosh, or ImageOptim to compress before uploading. Export from photo software at 80% quality rather than 100% (visually nearly identical, much smaller files).

For existing images: Use bulk compression plugins if you’re on WordPress (ShortPixel, Imagify, Smush) or Shopify (TinyIMG, Crush.pics). These can compress your existing 3,000 images automatically.

Format conversion: Convert JPEG/PNG to WebP. WebP is typically 25-35% smaller at the same quality. Most modern CMS can auto-convert or serve WebP to supported browsers.

Leo: Will compressing them hurt image quality? We have professional photography.

SDC SEO Brain: With proper compression, quality loss is imperceptible. The difference between a 2.4MB image and a 150KB optimized version isn’t visible to the human eye at web display sizes. You’re storing unnecessary data that only slows down your site without visual benefit. The exception: keep your original high-resolution files archived separately if you need them for print or other purposes.

Leo: What about the alt text issue? I think a lot of our images just have the product name.

SDC SEO Brain: Check a few product images. Right-click, inspect element, look for the alt attribute. What do they say?

Leo: Most are empty or just say the SKU number like “SKU-4829.”

SDC SEO Brain: That’s a significant SEO and accessibility problem. Alt text serves two purposes: it describes the image for screen readers (accessibility requirement) and tells Google what the image depicts (SEO signal). “SKU-4829” tells Google nothing. It should describe what’s in the image: “Brown wicker outdoor dining table with six matching chairs on a patio.”

Leo: That sounds time-consuming for 3,000 images.

SDC SEO Brain: It is, but it’s valuable work. Prioritize: start with your top-selling products and highest-traffic pages. For e-commerce, many platforms can auto-generate alt text from product name and attributes, like “[Product Name] – [Color] – [Material].” That’s better than empty alt text, though manually written descriptions are ideal for key images.

Leo: What makes good alt text?

SDC SEO Brain: Good alt text:

Describes the image accurately: What does the image show? A dining table? A close-up of the tabletop finish? Someone eating at the table?

Is specific but concise: 10-15 words typically. Long enough to be descriptive, short enough to be useful.

Naturally incorporates relevant terms: If the image shows an “outdoor teak dining table,” those words should appear because they describe what’s shown, not because you’re stuffing keywords.

Differs between images: If a product has 5 images from different angles, each alt should describe that specific view: “Front view of…”, “Close-up of tabletop showing…”, “Product dimensions diagram…”

Leo: What about the file names? Most of ours are like “DSC4829.jpg.”

SDC SEO Brain: File names should be descriptive and set before upload. Google uses file names as a relevance signal. “DSC4829.jpg” tells Google nothing. “teak-outdoor-dining-table-6-seater.jpg” tells Google exactly what the image shows.

For 3,000 existing images, renaming is painful and may break links. Prioritize going forward: rename all new uploads. For existing images, prioritize your top products. Some CMS platforms allow bulk renaming with redirects.

Leo: Do I need an image sitemap?

SDC SEO Brain: With 3,000 images, yes. An image sitemap helps Google discover all your images, especially if they’re loaded dynamically (JavaScript galleries, lazy loading). Most e-commerce platforms generate image sitemaps automatically, or plugins can create them. Submit to Search Console.

Leo: What about the structured data you mentioned?

SDC SEO Brain: For e-commerce, Product schema should include your product images. This can help your images appear in Google Shopping results and image-rich product listings. Recipe schema, if applicable, highlights images in recipe carousels. Make sure your product pages have proper Product schema with image property included.

Leo: Anything else for Google Images specifically?

SDC SEO Brain: A few more factors:

Context matters: Images rank partly based on the page they’re on. A well-optimized page about outdoor furniture helps your furniture images rank. Don’t orphan images on thin pages.

Original images rank better: Your professional product photography is valuable. Stock photos used on thousands of sites don’t rank well in Google Images because they’re not unique. Your unique product photos have an advantage.

Image placement: Images relevant to the main content, placed near relevant text, perform better than random decorative images.

Aspect ratio and quality: High-resolution, properly cropped images tend to rank better than blurry or awkwardly cropped ones. Google shows image previews, and quality affects click-through rate.

FAQ

Q: What’s the ideal alt text length?
A: 10-15 words or about 125 characters maximum. Long enough to describe the image meaningfully, short enough that screen readers don’t become tedious. Avoid very short alt text (“table”) and very long keyword-stuffed alt text.

Q: Do decorative images need alt text?
A: Decorative images (design elements, spacers, purely aesthetic) should have empty alt text (alt=””) so screen readers skip them. Images with informational content should always have descriptive alt text.

Q: What image format should I use?
A: WebP for most web images (best compression, good quality). JPEG as fallback for older browsers. PNG only when transparency is required. SVG for icons and logos. AVIF for cutting-edge performance if browser support isn’t critical.

Q: How much traffic can Google Images drive?
A: Varies dramatically by industry. Visual industries (fashion, home decor, food, travel, design) can see 20-40% of traffic from image search. Text-focused industries (B2B, finance, legal) see minimal image traffic. E-commerce typically benefits significantly.

Q: Should I lazy load images?
A: Yes for images below the fold. Lazy loading defers loading until images are about to be visible, improving initial page load speed. Don’t lazy load hero images or images visible on initial load (above the fold).

Summary

Image SEO has two goals: Ranking in Google Images and improving page performance for regular search. Both require optimization.

Alt text is the most important on-page factor. Describe what the image shows accurately and concisely. Empty or generic alt text is a missed opportunity. 10-15 words ideal.

File names are a ranking signal. Name files descriptively before upload: “red-leather-sofa.jpg” not “IMG4829.jpg”. Changing names after upload can break links.

Image file size affects page speed, which affects rankings:

Compress all images (target 50-200KB for most web images)
Use WebP format for best compression
Size images to display dimensions (don’t load 3000px image for 300px display)
Lazy load below-fold images

Image sitemaps help discovery. For sites with many images, especially dynamically loaded ones, submit an image sitemap to help Google find all images.

Context and page quality matter. Images rank based partly on the page they’re on. Optimize the full page, not just images.

Visual industries benefit most from image SEO. E-commerce, travel, food, design, fashion see significant traffic from Google Images. B2B and text-focused industries see less benefit.

Original images have advantages. Unique product photography or custom graphics rank better than stock photos used on many sites.

Sources

Google Search Central: Image SEO best practices – https://developers.google.com/search/docs/appearance/google-images
Google Search Central: Image sitemaps – https://developers.google.com/search/docs/crawling-indexing/sitemaps/image-sitemaps
Web.dev: Image optimization – https://web.dev/fast/

SDC SEO