How we got our results

Port80 Software conducts periodic surveys of Fortune 1000 corporate Web sites to discover if they are using HTTP compression technologies.

This survey is conducted between the first and fifteenth of a selected month and queries a list of 1000 leading global corporations' main corporate Web sites (e.g. Port80 Software queries this list of sites via a standard HTTP 1.1 GET request*, and the HTTP headers and any associated entity bodies (the target file is the resolved home page after redirects home page and it supporting elements, including frames, entry redirect pages, JavaScript includes, graphics, or CSS files) returned with the response are saved. The HTTP 1.1 GET request initially made includes the Accept-Encoding header to emulate a Web browser capable of receiving HTTP-compressed content (using either GZip or Deflate compression type acceptance definitions). The HTTP header responses to these requests are then analyzed for the Content-Encoding header to determine the number of sites that use HTTP compression.

Port80 Software then analyzes the data saved from these requests from each site in the list for total weight in bytes, taking into account all entity bodies downloaded. Using the popular GZip compression library found in Port80 Software's httpZip compression tool, all content from these downloads that can be compressed is optimized, and the resulting figures are recorded. Further analysis of the data allows for savings figures to be generated for the number or percentage of bytes saved and transmission speed improvement gained by using compression.

Real-time queries of the survey list or of any Web site using Port80 Software's "compression check" tool may provide different results on bytes and compression savings from those published by Port80 Software.

* HTTP 1.0 GET requests were used for the January 2003-August 2003 Surveys, and HTTP 1.1 GET requests were used for all surveys after September 2003.