PageSpeed Insights' analysis does not use real
devices. PageSpeed Insights fetches a site with a webkit
renderer (the same rendering engine that powers Chrome and Safari) that emulates both mobile device and desktop devices.
How does PageSpeed Mobile analysis
differ from regular PageSpeed analysis?
PageSpeed Mobile analyzes the mobile version of a page and
tailors suggestions based on the characteristics of mobile networks
and mobile devices. For instance, since mobile device CPUs are less
powerful than desktop CPUs, suggestions that reduce CPU consumption
the PageSpeed Mobile results.
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
How much does someone need to know
about web development before he/she can use PageSpeed Insights?
We assume that webmasters who are interested in improving
their site's performance will probably
have fairly advanced knowledge of web development techniques. Some PageSpeed Insights rules are based on basic
principles of web development; others are based on more advanced
features. It is helpful to have some knowledge of web hosting
documentation is also provided, so anyone can follow PageSpeed's
Why is PageSpeed Insights SDK open source?
We deeply believe in the importance of the open-source
model. By making PageSpeed open source, we allow anyone to see what
PageSpeed's performance rules check for, and to suggest improvements.
By encouraging feedback and patches, we believe that PageSpeed will
become more useful and accurate over time.
What rules is PageSpeed Insights based on? Who
created them? Why should someone trust them?
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
You spot a lot of errors in my page but
they conflict with the guidance I am getting from other site speed
tools. Why should I trust PageSpeed Insights more?
We would like to learn more on where you saw a discrepancy
between the tools.
Send a message to our discussion
Some of PageSpeed Insights' recommendations seem
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
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
Are there any restrictions in using
PageSpeed Insights technology?
The PageSpeed Insights code
base is governed by the Apache 2.0 Open Source License. You
can use PageSpeed Insights as determined and allowed by the license.
Why can't I find the PageSpeed Critical Path Explorer anymore?
The critical path explorer tool is no longer available as part of PageSpeed Insights.
Although the critical path is important for understanding web performance,
we have decided to re-think the feature in PageSpeed Insights. In the meantime, we suggest following
the recommendations under the new
PageSpeed Insights which lists the critical path resources for the page.