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High Performance Web Sites by Steve Souders

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Gzip in Action

Three examples for Rule 4 demonstrate the different degrees of compression you can deploy across your site.

In addition to the 48.6K HTML document, each example page contains a 59.9K stylesheet and a 68.0K script. Table 6-3 shows how the total page size varies with the amount of compression that is performed. Compressing the HTML document, stylesheet, and script reduces this page size from 177.6K to 46.4K, a size reduction of 73.8%! Compression typically reduces the content size by approximately 70%, but it varies depending on the amount of whitespace and character repetition.

Table 6-3. Page weight savings for different levels of compression

Example

Components (HTML, CSS, JS)

Total size

Size savings

Response time

Time savings

Nothing Gzipped

48.6K, 59.9K, 68.0K

177.6K

-

1562 ms

-

HTML Gzipped

13.9K, 59.9K, 68.0K

141.9K

34.7K (19.7%)

1411 ms

151 ms (9.7%)

Everything Gzipped

13.9K, 14.4K, 18.0K

46.4K

130.2K (73.8%)

731 ms

831 ms (53.2%)

The page with everything compressed loads ~831 milliseconds faster than the noncompressed example, a response time reduction of 53.2%. This was measured over a 900 Kbps DSL line. The absolute response time values vary depending on Internet connection, CPU, browser, geographic location, etc. However, the relative savings remain about the same. A simple change in your web server configuration, ...

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