Frequently Asked Questions

  1. How does PageSpeed Mobile analysis work? Does it use a real mobile device?
  2. I changed my site! Why doesn't PageSpeed Insights see the new version?
  3. Where do the PageSpeed Insights performance optimizations come from?
  4. PageSpeed Insights recommendations seem to conflict with the guidance I am getting from other site speed optimization tools. What should I do?
  5. Some of PageSpeed Insights' recommendations seem to go against certain design and development practices. Does Google think that only speed is important?
  6. Are PageSpeed Insights' recommendations more applicable to Google's applications than to the average website?
  7. Why am I seeing a captcha?
  8. Does the PageSpeed Insights score represent the real-world user experience?
Does PageSpeed Insights use a real device?
PageSpeed Insights' analysis does not use real devices. PageSpeed Insights fetches a site with a Blink renderer (the rendering engine that powers Google Chrome) that emulates both mobile device and desktop devices.
I changed my site! Why doesn't PageSpeed Insights see the new version?
PageSpeed Insights caches results for a short period of time. PageSpeed Insights should see any changes you've made within a few minutes.
Where do the PageSpeed Insights performance optimizations come from?
Many of the rules used by PageSpeed Insights came out of recommendations of blog posts and articles published by developers in the web community. Other rules were added by developers at Google based on research and internal use by Google applications.
PageSpeed Insights recommendations seem to conflict with the guidance I am getting from other site speed optimization tools. What should I do?
We would like to learn more on where you saw a discrepancy between the tools. Send a message to our discussion group .
Some of PageSpeed Insights' recommendations seem to go against certain design and development practices. Does Google think that only speed is important?
Since PageSpeed is a performance optimization tool, its recommendations are biased in favor of speed. However, we recognize that web development is complex, and our suggestions might be restrictive for an individual web site. You have to consider the tradeoffs for your own application: some of PageSpeed's recommendations take substantial effort to implement, so you need to evaluate the cost of making changes vs. the benefit the rule would have on your page. Our goal is simply to point out the issues that you should consider fixing.
Are PageSpeed Insights' recommendations more applicable to Google's applications than to the average website?
No. The advice given by PageSpeed is not specific to Google; it should improve the performance of any web page. Of course, pages that are slower have more to gain from PageSpeed's recommendations.
Why am I seeing a captcha?
PageSpeed Insights may occasionally show a captcha to confirm you are not a bot. If you are encountering a captcha when using the API, it may be due to the fact that you are using a shared API key. You can acquire an individual API Key by following these instructions.
Does the PageSpeed Insights score represent the real-world user experience?
PageSpeed Insights checks to see if a page has applied common performance best practices but does not account for all the factors that can affect a page's speed - e.g. type of the device used to access the page, network speed, and cache reuse of shared resources. As a result, while the score is correlated with the speed of a page, it is not completely representative of the real world user experience.