{"id":638,"date":"2026-07-03T12:45:19","date_gmt":"2026-07-03T07:15:19","guid":{"rendered":"https:\/\/imageoptimizerpro.ai\/blog\/?p=638"},"modified":"2026-07-03T12:48:47","modified_gmt":"2026-07-03T07:18:47","slug":"optimized-images-still-dont-improve-pagespeed-score","status":"publish","type":"post","link":"https:\/\/imageoptimizerpro.ai\/blog\/optimized-images-still-dont-improve-pagespeed-score\/","title":{"rendered":"Why Optimized Images Still Don’t Improve Your PageSpeed Score"},"content":{"rendered":"\n
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TL;DR:<\/strong> When optimized images still don’t improve PageSpeed score, the underlying issue is often elsewhere on the page. This article explains why PageSpeed Insights may continue reporting performance issues after image optimization and helps you identify the technical factors that have the greatest impact on loading speed, user experience, and Core Web Vitals.\n<\/p>\n<\/div>\n\n\n

Many website owners invest time in image performance optimization by compressing files, converting images to modern formats, and implementing responsive images<\/a>, expecting their PageSpeed score to improve.<\/p>\n\n

Then comes the surprise. You run another PageSpeed Insights test, only to find that the score has barely changed. One of the most common website performance issues is discovering that optimized images still don’t improve PageSpeed score<\/strong> as much as expected.<\/p>\n\n

The reason is simple: PageSpeed Insights evaluates the overall loading experience of a page, not just image files. While images play an important role, other factors can have a much bigger impact on performance and Core Web Vitals.<\/p>\n\n

<\/span>Quick Answer: Why Your PageSpeed Score Is Still Low After Image Optimization<\/span><\/h2>\n

Optimizing images improves only one part of website performance. PageSpeed Insights also measures factors like JavaScript execution, render-blocking CSS, server response times, layout stability, and third-party scripts. If these issues remain, your PageSpeed score may stay low even after image optimization. <\/p>\n\n

\n\n \n \n \n \n \n \n \n \n \n \n \n
Common Issue<\/th>\n Effect on PageSpeed<\/th>\n <\/tr>\n <\/thead>\n
Excessive JavaScript<\/td>\n Delays rendering, interactivity, and Core Web Vitals metrics<\/td>\n <\/tr>\n
Incorrect LCP Element Optimization<\/td>\n The actual Largest Contentful Paint element remains slow<\/td>\n <\/tr>\n
Slow Server Response Times<\/td>\n Delays the loading of all page resources<\/td>\n <\/tr>\n
Render-Blocking CSS and Fonts<\/td>\n Prevents content from rendering quickly<\/td>\n <\/tr>\n
Unprioritized Images<\/td>\n Critical above-the-fold images load too late<\/td>\n <\/tr>\n
Misinterpreting PageSpeed Data<\/td>\n Strong lab results may hide poor real-user performance<\/td>\n <\/tr>\n
Layout Shift Issues (CLS)<\/td>\n Reduces visual stability and user experience<\/td>\n <\/tr>\n
Third-Party Scripts<\/td>\n Add extra network requests and processing overhead<\/td>\n <\/tr>\n <\/tbody>\n<\/table>\n<\/div>\n\n

In short, image optimization<\/a> is important, but it is rarely the only factor affecting PageSpeed Insights scores. Modern performance metrics evaluate the entire loading experience, including JavaScript, server performance, Core Web Vitals<\/a>, resource prioritization, and user interactions.<\/p>\n\n

<\/span>How PageSpeed Insights Calculates Your Performance Score <\/span><\/h2>\n

Before troubleshooting image optimization not improving PageSpeed, it’s important to understand what PageSpeed Insights actually measures<\/a>.<\/p>\n\n

Google’s PageSpeed Insights uses Lighthouse performance audits and evaluates multiple metrics, including:<\/p>\n

\n\n \n \n \n \n \n \n \n \n \n
Metric<\/th>\n What It Measures<\/th>\n <\/tr>\n <\/thead>\n
Largest Contentful Paint (LCP)<\/td>\n Loading speed of the main visible content<\/td>\n <\/tr>\n
Interaction to Next Paint (INP)<\/td>\n Responsiveness after user interaction<\/td>\n <\/tr>\n
Cumulative Layout Shift (CLS)<\/td>\n Visual stability<\/td>\n <\/tr>\n
First Contentful Paint (FCP)<\/td>\n Initial content rendering<\/td>\n <\/tr>\n
Speed Index<\/td>\n Visual loading progress<\/td>\n <\/tr>\n
Total Blocking Time (TBT)<\/td>\n Time blocked by JavaScript execution<\/td>\n <\/tr>\n <\/tbody>\n<\/table>\n<\/div>\n\n

According to Google Lighthouse<\/a>, Largest Contentful Paint (LCP), Total Blocking Time (TBT) in lab testing, and Cumulative Layout Shift (CLS) contribute significantly to Lighthouse performance scores. For real-user performance, Interaction to Next Paint (INP) replaces TBT as the responsiveness metric in Core Web Vitals.<\/p>\n\n\n

This is why image optimization and PageSpeed Insights<\/strong> do not always correlate as directly as many website owners expect.<\/p>\n\n\n

<\/span>Start With an Image Optimization Reality Check<\/span><\/h2>\n

If PageSpeed Insights is still reporting oversized images, next-generation format recommendations<\/a>, or improper image sizing, those issues should be fixed before investigating non-image issues. Many websites believe their images are optimized when PageSpeed Insights still detects image-related opportunities.<\/p>\n\n

\n\n \n \n \n \n \n \n \n \n \n
Optimization Area<\/th>\n What to Check<\/th>\n <\/tr>\n <\/thead>\n
Compression<\/td>\n Images are compressed without noticeable quality loss<\/td>\n <\/tr>\n
Modern Formats<\/td>\n WebP or AVIF is used where supported<\/td>\n <\/tr>\n
Proper Sizing<\/td>\n Images are not significantly larger than their display dimensions<\/td>\n <\/tr>\n
Responsive Images<\/td>\n srcset<\/code> and responsive image delivery are implemented<\/td>\n <\/tr>\n
Lazy Loading<\/td>\n Offscreen images load only when needed<\/td>\n <\/tr>\n
Image Dimensions<\/td>\n Width and height attributes are specified<\/td>\n <\/tr>\n <\/tbody>\n<\/table>\n<\/div>\n\n

If PageSpeed Insights continues surfacing image-related opportunities, addressing those PageSpeed Insights recommendations<\/a> should be your first priority before investigating broader performance issues.<\/p>\n\n\n

<\/span>Common Causes of Low PageSpeed Scores Beyond Image Optimization<\/span><\/h2>\n

If your images are already compressed, properly sized, and served in modern formats like WebP and AVIF<\/a>, other performance issues may be preventing meaningful PageSpeed improvements. The following are the most common causes.\n<\/p>\n\n\n

Reason 1: JavaScript Is Slowing Down Your Site<\/h3>\n

Even when images are fully optimized, excessive JavaScript can significantly impact PageSpeed performance. Large scripts can block the browser’s main thread, delaying rendering, interactivity, and Core Web Vitals metrics.<\/p>\n\n

Common Causes<\/strong><\/h4>\n