Image Optimization Audit: What to Check

Images play a crucial role in both user experience and SEO. However, many websites struggle with slow-loading pages, missing alt text, and other image optimization issues. By conducting a thorough image optimization audit, you can identify and fix these problems to boost your search rankings, traffic, and engagement. In this guide, we'll walk through 15 key factors to check in your image optimization audit.

Optimizing your images delivers substantial benefits:

• Faster page load times
• Better user experience
• Improved search engine crawlability
• More ranking opportunities in image search
• Increased engagement and conversions

Ready to upgrade your image SEO? Let's dive into the essential elements of an image optimization audit.

1. File Format

Using the right file format is critical for image performance. The three most common web image formats are:

• JPEG: Best for photographs and complex images with many colors.
• PNG: Ideal for simpler images like logos, illustrations, and images with transparency.
• WebP: A modern format that offers better compression than JPEG and PNG while maintaining quality.

In general, use JPEG for photos, PNG for graphics, and consider WebP for even better performance. Avoid other formats like GIF or TIFF unless absolutely necessary.

2. File Size

Large image files slow down your pages, harming user experience and SEO. Audit your images to ensure they are optimized for the web:

• Aim for under 100 KB per image, especially for thumbnails and small images.
• For hero images or large photos, keep them under 1 MB.
• Use image compression tools to reduce file size without sacrificing quality.
• Remove unnecessary metadata like camera information from photos.

By reducing image file sizes, you'll significantly improve page load times and user experience.

3. Image Dimensions

Serving images at the correct dimensions is crucial for performance. Follow these best practices:

• Resize images to the exact dimensions needed on the page.
• Avoid using HTML or CSS to scale down large images - resize them beforehand.
• Consider using responsive images to serve different sizes based on screen size.
• Use image thumbnails for gallery pages or product listings.

Properly sized images load faster and use less bandwidth, improving page speed and user experience.

4. Compression

Image compression reduces file size while maintaining acceptable quality. There are two main types:

• Lossy compression: Removes some image data to achieve smaller file sizes. Slightly reduces quality but usually not noticeable. Formats like JPEG and WebP use lossy compression.
• Lossless compression: Reduces file size without losing any data or quality. Ideal for simpler images like logos or graphics. PNG uses lossless compression.

For most web images, lossy compression with a quality setting of 70-85% provides a good balance of size and quality. Tools like Adobe Photoshop, TinyPNG, and Squoosh make it easy to compress images.

5. Lazy Loading

Lazy loading defers the loading of offscreen images until the user scrolls near them. This technique:

• Improves initial page load times
• Reduces bandwidth usage
• Provides a smoother user experience

Many websites, including ecommerce sites and blogs, can benefit from lazy loading. You can implement it using JavaScript libraries or built-in browser support. Audit your pages to ensure lazy loading is working correctly and not causing any display issues.

6. Responsive Images

Responsive images adapt to different screen sizes and devices, providing a better user experience. Techniques include:

• Using the srcset and sizes attributes to specify multiple image versions
• Serving different image crops or aspect ratios based on screen size
• Using CSS media queries to style images differently on various devices

Audit your site to ensure you're using responsive images effectively. Check that the correct image versions load on different devices and that the layout remains visually appealing.

7. Alt Text

Alt text provides a text alternative for images, which is crucial for accessibility and SEO. When auditing your images, ensure that:

• All important images have descriptive, accurate alt text.
• Alt text is concise but includes relevant keywords.
• Decorative images have empty alt attributes (alt="") to avoid confusion.
• Alt text makes sense when read out of context.

Good alt text helps visually impaired users understand your content and gives search engines more context about your images.

8. File Names

Descriptive, keyword-rich file names can boost your image SEO. When auditing your images:

• Use descriptive names that include relevant keywords.
• Separate words with hyphens, not underscores or spaces.
• Keep file names concise - aim for under 60 characters.
• Avoid generic names like "image1.jpg" or "pic.png".

Well-optimized file names help search engines understand your images and can improve your rankings in image search results.

9. Structured Data

Structured data, like Schema.org markup, provides additional context about your images to search engines. When relevant, consider adding structured data for:

• Products: Use Product schema to specify details like price, availability, and review ratings.
• Recipes: Use Recipe schema to include ingredients, instructions, and nutrition information.
• Videos: Use VideoObject schema to provide details like title, description, and thumbnail URL.

Structured data can enhance your appearance in search results and make your images more likely to appear in rich snippets.

10. Image Sitemaps

An image sitemap helps search engines discover and index your images. It provides additional details like:

• Image URL
• Title or caption
• Description or alt text
• License information
• Geographic location

If you have a large site with many images, consider creating a separate image sitemap. Submit it to Google Search Console to ensure your images are being crawled and indexed properly.

11. Mobile Optimization

With mobile devices accounting for over 50% of web traffic, it's crucial to optimize your images for smaller screens. When auditing your images for mobile:

• Ensure images scale properly and don't overflow the screen.
• Use responsive images to serve smaller file sizes on mobile.
• Lazy load images to improve initial page load times.
• Optimize for touch screens with larger tap targets and easy zooming.

By providing a great mobile image experience, you'll improve user engagement and mobile search rankings.

12. Content Delivery Network (CDN)

A CDN can significantly improve image loading times by serving images from servers closer to the user. Benefits include:

• Reduced latency and faster load times
• Lower bandwidth costs
• Improved scalability and reliability
• Built-in image optimization and resizing

If you have a global audience or a high-traffic site, consider using a CDN to deliver your images. Popular options include Cloudflare, Amazon CloudFront, and Akamai.

13. Caching

Caching stores frequently accessed images in the user's browser or on the server, reducing the need to reload them on subsequent visits. When auditing your image caching:

• Ensure images have appropriate Cache-Control and Expires headers.
• Use a unique filename for each image version to avoid serving stale cache.
• Consider using a plugin or service to automatically optimize and cache images.

Proper caching can significantly improve image load times and reduce server load.

14. Accessibility

In addition to alt text, there are other ways to make your images more accessible:

• Provide captions or transcripts for complex images or infographics.
• Ensure sufficient color contrast between text and background images.
• Avoid using images of text, which can be difficult to read and translate.
• Use CSS for decorative images and icons instead of embedding them in the HTML.

By making your images accessible, you'll provide a better experience for all users and demonstrate a commitment to inclusivity.

15. Performance Testing

Regular performance testing can help you identify image optimization issues before they impact users. Tools to consider:

• Google PageSpeed Insights: Analyzes your pages and provides suggestions for improving image performance.
• Lighthouse: Audits your site for performance, accessibility, and SEO, including image optimization.
• WebPageTest: Provides detailed performance metrics and waterfall charts to help identify slow-loading images.

By regularly testing your image performance and making data-driven optimizations, you'll provide a faster, more engaging user experience.

Putting Your Image Optimization Audit into Action

Conducting a comprehensive image optimization audit is the first step to improving your website's performance and search rankings. By addressing these 15 key factors, you'll be well on your way to faster, more user-friendly pages.

Remember, image optimization is an ongoing process. As you add new content and make updates, be sure to follow best practices and regularly audit your images. With a commitment to continuous improvement, you'll provide a better experience for your users and stay ahead of the competition in search results.