High Performance Web Sites

Chapter 6. Rule 4: Gzip Components

The time it takes to transfer an HTTP request and response across the network can be significantly reduced by decisions made by frontend engineers. It's true that the end user's bandwidth speed, Internet service provider, proximity to peering exchange points, and other factors are beyond the control of the development team. However, there are more variables that affect response times. Rules 1 and 3 address response times by eliminating unnecessary HTTP requests. If there is no HTTP request then there is no network activity—the ideal situation. Rule 2 improves response times by bringing the HTTP response closer to the user.

Rule 4, examined in this chapter, reduces response times by reducing the size of the HTTP response. If an HTTP request results in a smaller response, the transfer time decreases because fewer packets must travel from the server to the client. This effect is even greater for slower bandwidth speeds. This chapter shows how to use gzip encoding to compress HTTP responses, and thus reduce network response times. This is the easiest technique for reducing page weight and it also has the biggest impact. There are other ways you can reduce the HTML document's page weight (strip comments and shorten URLs, for example), but they are typically less effective and require more work.

How Compression Works

The same file compression that has been used for decades to reduce file sizes in email messages and on FTP sites is also used to deliver compressed ...