The GZIP functionality will allow you to compress the HTML output of forum pages and reduce the bandwidth usage.

You can turn on the corresponding functionality and set the compression level from your vBulletin admin control panel->Settings->Options->Cookies and HTTP Header Options.

You can check whether the GZIP compression is supported on your server by following the solution published in our Knowledge Base article:

http://kb.siteground.com/article/How_to_enable_gZIP_compression_for_your_pages.html