HOW TO: Enable ASPX Compression in IIS

This step-by-step article describes how to configure Internet Information Services (IIS) 5.0 to compress .aspx pages. To use .aspx pages, you must have the ASP.NET page framework installed. You add the compression functionality for .aspx files by editing the IIS metabase.

HTTP Compression

HTTP compression provides faster transmission time between compression-enabled browsers (Microsoft Internet Explorer 5.0 or later) and IIS. You can either compress static files alone, or both static files and applications. If your network bandwidth is restricted, consider HTTP compression, at least for static files, unless your processor utilization is already extremely high.

When IIS receives a request, it checks to see if the browser is compression-enabled. IIS then checks the file name extension to see if the requested file is a static file or contains dynamic content. If the file contains static content, IIS checks to see if the file has previously been requested and is already stored in a compressed format in the temporary compression directory. If the file is not stored in a compressed format, IIS sends the uncompressed file to the browser, and adds a compressed copy of the file to the temporary compression directory. If the file is stored in a compressed format, IIS sends the compressed file to the browser. No files are compressed until they have been requested one time by a browser.

If the file contains dynamic content, IIS compresses the file as it is generated and sends the compressed file to the browser. No copy of the file is stored.

The cost of compressing a static file is modest and is typically incurred only one time, because the file is then stored in the temporary compression directory. The cost of compressing dynamically generated files is a little higher, because they are not stored and must be regenerated with each request. The cost of expanding the file at the browser is minimal. Compressed files download faster, so are particularly beneficial to the performance of any browser that uses a network connection with restricted bandwidth (a modem, for example).

Edit the Metabase

WARNING: If you edit the metabase incorrectly, you can cause serious problems that may require you to reinstall any product that uses the metabase. Microsoft cannot guarantee that problems that result if you incorrectly edit the metabase can be solved. Edit the metabase at your own risk.

NOTE: Always back up the metabase before you edit it.

To enable IIS 5.0 to compress .aspx pages, follow these steps:

1. Open a command prompt.
2. Type net stop iisadmin, and then press ENTER.
3. Type cd C:\InetPub\adminscripts, and then press ENTER.
4. Type the following, and then press ENTER:
   CSCRIPT.EXE ADSUTIL.VBS SET W3Svc/Filters/Compression/GZIP/HcScriptFileExtensions "asp" "dll" "exe" "aspx"
5. Type the following, and then press ENTER:
   CSCRIPT.EXE ADSUTIL.VBS SET W3Svc/Filters/Compression/DEFLATE/HcScriptFileExtensions "asp" "dll" "exe" "aspx"
6. Type net start w3svc, and then press ENTER.

For more information about compression, see the IIS 5.0 online documentation at the following Microsoft Web site: