WordPress Image Optimization for SEO: Complete Checklist

Images are crucial for user engagement, but improperly optimized images can destroy your SEO. This comprehensive checklist covers everything you need to know about WordPress image optimization for search engines in 2025.

Why Image Optimization Matters for SEO

Google's algorithm considers multiple image-related factors when ranking pages:

• Page Speed: Large, unoptimized images slow down your site. Page speed is a direct ranking factor.
• Image Search: Google Images drives significant traffic. Properly optimized images rank higher in image search results.
• User Experience: Fast-loading, properly sized images reduce bounce rate, which impacts rankings.
• Mobile Performance: With mobile-first indexing, image optimization is critical for mobile users.

The Complete Image SEO Checklist

File Format Selection

Choosing the right image format is the foundation of optimization. Learn how to convert your WordPress images to WebP.

File Size Optimization

Actionable steps:

• Compress images before uploading (use tools like TinyPNG or Altomatic)
• Set WordPress to generate appropriately sized thumbnails
• Avoid uploading images larger than they'll be displayed
• Use responsive images with srcset attributes

Descriptive Alt Text

Alt text is one of the most important on-page SEO factors for images. If you have hundreds of images, learn how to bulk add alt text to WordPress images.

Alt text best practices:

• Keep it under 125 characters (screen reader sweet spot)
• Include target keywords when relevant and natural
• Describe the image's content and purpose
• Skip "image of" or "picture of" - screen readers announce it's an image
• Leave alt text empty for purely decorative images

Descriptive File Names

File names are a ranking factor. Rename images before uploading.

• Use descriptive, keyword-rich file names
• Separate words with hyphens, not underscores
• Use lowercase letters
• Keep names concise but descriptive

Image Dimensions

Never upload images larger than they'll be displayed on your site.

Common WordPress image sizes:

• Hero images: 1920px × 1080px (max)
• Featured images: 1200px × 630px
• Blog post images: 800px × 600px
• Thumbnails: 300px × 300px

Lazy Loading

WordPress includes native lazy loading since version 5.5. Images load only when users scroll to them.

Verify lazy loading is active:

• WordPress adds loading="lazy" automatically to images
• Check your page source to confirm
• For older WordPress versions, use a lazy loading plugin
• Exclude above-the-fold images from lazy loading

Image CDN (Content Delivery Network)

CDNs serve images from servers closest to your users, dramatically improving load times globally.

• Use a CDN like Cloudflare, BunnyCDN, or StackPath
• Or use WordPress-specific CDNs (Jetpack, WP Rocket)
• Most optimization plugins include CDN features
• Typical speed improvement: 40-60% for international users

Responsive Images

WordPress automatically generates multiple image sizes and uses srcset. Verify it's working correctly.

Check your responsive images:

• Inspect an image on your site (right-click → Inspect)
• Look for srcset attribute with multiple image sizes
• If missing, check theme or page builder settings
• Ensure your theme supports responsive images properly

Image Sitemap

Help Google discover and index all your images with an image sitemap.

• Use Yoast SEO or Rank Math to auto-generate image sitemaps
• Submit your sitemap to Google Search Console
• Verify images are being indexed in GSC → Coverage report
• Update sitemap whenever you add new images

Structured Data for Images

Add schema markup to help search engines understand your images better.

• Use ImageObject schema for important images
• Include for product images, recipe photos, article images
• Most SEO plugins add this automatically
• Test with Google's Rich Results Test tool

Common WordPress Image SEO Mistakes

How to Audit Your Current Images

Before optimizing, audit your existing images to understand what needs fixing.

1. Use Google PageSpeed Insights

• Test your homepage and top pages
• Look for "Properly size images" and "Serve images in next-gen formats"
• Note specific images that need optimization

2. Check Google Search Console

• Go to Coverage → Image results
• See how many images Google has indexed
• Check for image indexing errors

3. Review Your Media Library

• Go to Media → Library in WordPress
• Check random images for alt text
• Look at file sizes (anything over 200KB needs optimization)
• Verify file names are descriptive

Quick Wins: Do These First

If you're overwhelmed, start with these high-impact, quick tasks:

1. Install an image optimization plugin

   Automate compression and format conversion for future uploads

2. Add alt text to your top 20 pages

   Focus on your most-visited content first

3. Convert hero images to WebP

   Above-the-fold images have the biggest impact on Core Web Vitals

4. Enable lazy loading

   Built into WordPress 5.5+, just verify it's working

5. Submit image sitemap

   2 minutes of work for better image indexing

Measuring Success

Track these metrics to see the impact of your image optimization:

• Google PageSpeed Insights score: Aim for 90+ on mobile
• Largest Contentful Paint (LCP): Should be under 2.5 seconds
• Total page size: Target under 1MB for most pages
• Image search traffic: Check Google Search Console → Performance → Image
• Bounce rate: Should decrease as pages load faster