What Tools Are Best For Auditing Image Performance?

Story Based Question

You’re managing a website for an e-commerce store that sells gadgets. The site features a lot of high-quality product images and you’ve noticed that the page load times are slower than expected. Since these delays could be hurting your sales and SEO, you want to identify and fix any issues related to image performance. What tools should you use to audit the performance of images on the website?

Exact Answer

To audit image performance, you can use tools like Google PageSpeed Insights, Lighthouse, WebPageTest, and GTmetrix. These tools provide detailed insights into image optimization, identifying issues like large file sizes, inefficient formats, and unoptimized image loading techniques. They also offer actionable suggestions to improve image performance.

Explanation

Auditing image performance is a crucial step in identifying what’s slowing down your website and negatively impacting user experience and SEO. Several tools can help you evaluate and optimize images for faster loading times and improved efficiency. Here’s a breakdown of the best tools for auditing image performance:

1. Google PageSpeed Insights: This is one of the most popular tools for measuring website performance, including image optimization. It provides a detailed report on your site’s performance and identifies opportunities for image improvement, such as large image files or outdated formats. It also suggests improvements, like converting images to next-gen formats like WebP or implementing lazy loading.
2. Lighthouse: A part of Chrome DevTools, Lighthouse is an open-source tool that audits web pages for performance, accessibility, SEO, and more. It includes specific metrics for image optimization, such as serving responsive images, compressing large files, and lazy loading. Lighthouse gives a detailed report on how images affect overall page speed and offers detailed suggestions to improve them.
3. WebPageTest: WebPageTest allows you to test your site’s performance from different locations and on different devices. It provides a waterfall chart that shows how resources, including images, are loaded. This helps you understand how images impact page load times and where bottlenecks occur. The tool also identifies if images are blocking the page’s rendering, which can help you prioritize optimizations like lazy loading or deferring non-essential images.
4. GTmetrix: GTmetrix is another popular performance auditing tool that provides a detailed breakdown of your site’s performance. It evaluates various aspects of your website, including image size, format, and optimization. GTmetrix offers recommendations for image-related improvements, like reducing image dimensions, compressing files, and using the right image formats.
5. WebP Inspector (for format optimization): If you want to check whether you’re using WebP images or need to convert your current images to WebP for better performance, WebP Inspector is a handy tool. It helps you identify images that could benefit from being served in WebP format and checks their compatibility across different browsers.

Example

Let’s say you’re auditing the e-commerce website that sells gadgets, and you want to improve the performance of product images. Here’s how you can use these tools to get actionable insights:

1. Using Google PageSpeed Insights:
   • You run the website through PageSpeed Insights and discover that many of the product images are too large (over 2MB each). PageSpeed Insights suggests compressing these images and converting them to the WebP format for better performance. It also recommends serving smaller images for mobile devices.
2. Using Lighthouse:
   • Running the website through Lighthouse, you find that the images aren’t responsive. The same large images are being served to desktop and mobile users, even though mobile screens only need smaller images. Lighthouse recommends implementing srcset for responsive image delivery to serve appropriately sized images based on the device.
3. Using WebPageTest:
   • WebPageTest shows a waterfall chart where you notice that product images are loading after other resources like CSS and JavaScript. The tool highlights that the images aren’t being lazy-loaded, causing delays in page rendering. You decide to implement lazy loading so that images load only when they enter the viewport.
4. Using GTmetrix:
   • GTmetrix points out that some images are in PNG format, which is not as efficient as WebP. It also highlights large image sizes and suggests compressing them without sacrificing quality. GTmetrix recommends converting the images to WebP for better performance.

By using these tools, you discover that the product images on your site are too large and not optimized for mobile users. You take action by compressing the images, converting them to WebP format, implementing lazy loading, and using srcset for responsive images. These changes result in a significant performance improvement, leading to faster load times and a better user experience.

By using tools like Google PageSpeed Insights, Lighthouse, WebPageTest, GTmetrix, and WebP Inspector, you can identify and fix image-related performance issues, improving load times and overall site performance.