Page Speed is a Firefox/Firebug Add-on. It runs a number of diagnostic tests against a web page,
and analyzes the page's performance on a number of "rules" that are known to speed up page load time.
The rules are based on general principles of web page performance, including resource caching, data upload
and download size, and client-server round-trip times. They examine factors such as web server configuration,
JavaScript and CSS code, image file properties, and so on. For each rule, Page Speed gives a general score,
using a simple red-yellow-green grading scheme, and suggests specific techniques for correctly implementing
each rule. It also provides some automatic optimization of external resources included on a page,
such as minifying JavaScript code and compressing images.
How much does someone need to know about web development before he/she can use Page Speed?
We assume that webmasters who are interested in improving their site's performance will probably
have fairly advanced knowledge of web development techniques. Some Page Speed 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 technologies, HTTP, JavaScript and CSS. However, extensive documentation
is also provided, so anyone can follow Page Speed's recommendations.
Why did you release Page Speed as open source?
We deeply believe in the importance of the open-source model. By making Page
Speed open source, we allow anyone to see what Page Speed's performance rules check for,
and to suggest improvements. By encouraging feedback and patches, we believe
that Page Speed will become more useful and accurate over time.
What rules is Page Speed based on? Who created them? Why should someone trust them?
Many of the rules used by Page Speed 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.
How is Page Speed different from YSlow?
YSlow is a great product from Yahoo! and there are a number of other tools available that help optimize pages for speed.
Anything that helps webmasters design faster sites is a benefit to everyone. YSlow and Page Speed use some common "rules"
that are based on industry best practices. There are, however, some rules, such as deferring JavaScript until after
the page has loaded, that Page Speed implements exclusively. In addition, Page Speed provides you with an activity
panel that allows you to do a "before and after" comparison when considering the implementation of Page Speed's
suggestions. Finally, Page Speed is an open-source tool that is open to community contributions.
I am using YSlow now. Can I also use Page Speed?
Yes. We hope webmasters can benefit from both.
You spot a lot of errors in my page but they conflict with the guidance I am getting from other site speed optimization
tools. Why should I trust Page Speed more?
We would like to learn more on where you saw a discrepancy between the two tools.
Send a message to our discussion group or file a bug
in our issue tracker.
Why is the download so large (1.6 MB)?
Page Speed includes some C++ native libraries, such as those used
for image compression, that need to be compiled for each of the five platforms
that we support. Rather than having 5 separate downloads, we bundle the libraries for all platforms in a single download.
Why is Page Speed not available for Chrome?
When we started writing Page Speed, Chrome did not exist. There is currently
no way to write an extension for Chrome, although the Chrome developers are
working on an extensions API. (See the
Chrome
Developer Documentation Extensions wiki page for more information.) When the
extensions API is available, we will consider porting Page Speed to Chrome.
Some of Page Speed's recommendations seem to go
against certain design and development practices. Does Google think
that only speed is important?
Since Page Speed 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 Page Speed'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 Page Speed's recommendations more applicable to Google's applications than to the average website?
No. The advice given by Page Speed 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 Page Speed's recommendations.
Are Page Speed's recommendations more applicable to
applications developed with the Google Web Toolkit (GWT) rather than
with handwritten JavaScript code?
No. GWT makes it harder to make some mistakes that Page Speed
catches, so if anything, it should be more useful to non-GWT users.
In fact, we used Page Speed internally to evaluate and improve Google
properties, most of which do not use GWT.
Is Page Speed suitable for mobile sites?
Yes.
Are there any restrictions in using Page Speed technology?
The Page Speed code base is governed by the Apache 2.0 Open Source License.
You can use Page Speed as determined and allowed by the license.
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