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Why WP Fastest Cache Might Not Improve Your PageSpeed Score (And How to Fix It)

38 threads Sep 16, 2025 Plugin → Wp fastest cache

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Many WordPress users turn to caching plugins like WP Fastest Cache to boost their site's performance and PageSpeed scores. However, it's a common and sometimes confusing experience to run a speed test after installation and see little to no improvement, or even a decline in metrics. This article explores the most frequent reasons for this discrepancy and provides actionable solutions based on community discussions.

Why This Happens

PageSpeed Insights (PSI) and other testing tools like GTmetrix simulate a first-time visitor's experience. They measure metrics such as Largest Contentful Paint (LCP) and First Contentful Paint (FCP). A caching plugin's primary job is to serve a static HTML file, which drastically reduces server response time. However, these tools also grade other factors that caching alone may not address, such as:

  • Unoptimized images (large file sizes, incorrect dimensions)
  • Render-blocking resources (CSS and JavaScript)
  • Unused CSS or JavaScript
  • The loading of third-party resources (e.g., Google APIs, Facebook Pixel)
  • Issues specifically with the mobile version of a site

Furthermore, if a test is run on a page that hasn't been cached yet, the results will not reflect the plugin's benefits.

Common Scenarios and Solutions

1. The Test Was Run on an Uncached Page

The Problem: The most common reason for not seeing an improvement is simply testing the wrong page. Speed tests must be run on a page that has already been generated and cached by the plugin.

The Solution: Always clear your site's cache after changing settings. Then, visit your homepage and a few other key pages once in a browser to trigger the cache creation. Afterward, run your PageSpeed test again on the specific URL you visited.

2. The Real Bottleneck Is Elsewhere

The Problem: Your server response time might already be excellent, but other issues are dragging down your score. Caching improves TTFB (Time to First Byte), but it doesn't fix massive images or render-blocking code. Threads show users often see warnings for "Reduce Unused CSS" or "Properly Size Images" regardless of their cache setup.

The Solution: Use the PageSpeed Insights report as a guide. Focus on addressing its specific recommendations:

  • Images: Compress and resize images before uploading. Consider using a dedicated image optimization plugin.
  • Render-blocking Resources: While WP Fastest Cache can minify and combine CSS/JS, for more advanced control like critical CSS generation, you may need additional optimization tools.
  • Mobile vs. Desktop: Scores for mobile are typically lower and harder to optimize. The free version of WP Fastest Cache does not create a separate mobile cache for responsive themes, which can sometimes lead to slower mobile performance as noted in several threads.

3. Plugin or Hosting Conflicts

The Problem: Conflicts with other plugins or specific hosting environments can prevent WP Fastest Cache from working correctly. For example, using multiple caching plugins simultaneously will cause problems. Some hosts, like WP Engine, have their own caching layers that need to be configured in tandem.

The Solution:

  • Disable other caching or optimization plugins one by one to test for conflicts.
  • If you are on a managed host, check their documentation for recommended cache plugin settings. Often, you only need to enable the "Cache System" option.
  • As a general rule, enable all options in the free version and test. If problems arise, disable features one by one to identify the culprit (e.g., Minify CSS/HTML, Lazy Load).

4. Misunderstanding the Results

The Problem: A score in the 70s or 80s is often already good. Caching plugins are not magic bullets that will guarantee a perfect 100; they are one part of a larger performance strategy. A decline from 87 to 77, as reported in one thread, is unusual and typically points to a specific conflict or a test run on an uncached page.

The Solution: Look beyond the overall score. Check the specific metrics for "Server Response Time" and "First Contentful Paint." If these have improved, then the cache is working. Your effort should then shift to tackling the next set of issues highlighted in the report.

Conclusion

Seeing no change in your PageSpeed score after installing WP Fastest Cache can be frustrating, but it's usually a solvable problem. The key takeaways are to always test on a cached page, use the detailed speed report to guide your optimization efforts beyond caching, and ensure your plugin settings are compatible with your hosting environment and other plugins. By methodically addressing these areas, you can leverage WP Fastest Cache to its full potential as a foundation for a faster website.

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