Web Performance Best Practices

When you profile a web page with Page Speed, it evaluates the page's conformance to a number of different rules. These rules are general front-end best practices you can apply at any stage of web development. We provide documentation of each of the rules here, so whether or not you run the Page Speed tool — maybe you're just developing a brand new site and aren't ready to test it — you can refer to these pages at any time. We give you specific tips and suggestions for how you can best implement the rules and incorporate them into your development process.

About the performance best practices

Page Speed evaluates performance from the client point of view, typically measured as the page load time. This is the lapsed time between the moment a user requests a new page and the moment the page is fully rendered by the browser. The best practices cover many of the steps involved in page load time, including resolving DNS names, setting up TCP connections, transmitting HTTP requests, downloading resources, fetching resources from cache, parsing and executing scripts, and rendering objects on the page. Essentially Page Speed evaluates how well your pages either eliminate these steps altogether, parallelize them, and shorten the time they take to complete. The best practices are grouped into five categories that cover different aspects of page load optimization:

• Optimizing caching — keeping your application's data and logic off the network altogether
• Minimizing round-trip times — reducing the number of serial request-response cycles
  
• Minimizing request overhead — reducing upload size
• Minimizing payload size — reducing the size of responses, downloads, and cached pages
  
• Optimizing browser rendering — improving the browser's layout of a page

Send us your feedback

We would appreciate any feedback you would like to give about the rules described in these pages. If you have suggestions on how to make these best practices better (or how to document them better!), post them to our discussion group at page-speed-discuss.

Additional resources

• For more detailed information on many of the best practices described in these pages, see Steve Souders' High Performance Web Sites and Even Faster Web Sites.
• For running code examples that illustrate the techniques described in these pages, see the companion website, 14 Rules for Faster-Loading Web Sites.
• For a runnable test and summary comparison of browsers' behavior on many of the metrics discussed in these pages, see Browserscope.