We support two canonical name redirection settings:
off - Our system attempts to avoid the use of a site's canonical name. Redirects issued by the network will use the hostname presented in the HTTP Host: header. From an application standpoint this means that the HTTP_HOST variable will be copied to the SERVER_NAME variable for each request. This setting is particularly suited to sites that vary their content based on which alias is used, such as WordPress multi-site hosting, or if you want to use our per-alias document root feature to host multiple websites using only one site on our system.
on - If anybody accesses your site using an alias other than its canonical name, will automatically, transparently get a "301 Moved Permanently" redirect to the correct name. This setting is particularly appropriate for sites with one correct name, but a number of other aliases that the site owner also wishes to accept.
Your site's canonical name and type settings are visible in the "Config Information" box on the Site Information page for that site. To make changes to your site's canonical name or type settings, use the "Edit" button on the "Canonical URL" line.
If you are running software on your site that lets you designate the official URL for the site (such as WordPress), you'll need to update that information before you enable canonical name redirection to a name that is different from what your software is expecting. If you don't, your software and our system will get into a slap fight over what name is correct, and all visitors to your site will get is a "too many redirects" error.
If that happens, switch the canonical type back to "off" to let your site load and regain access to your software's administration area. (To continue with the WordPress example, the "blog URI" or "WordPress address (URL)" is the software setting in question.)
For more information about canonical names, see this FAQ entry.(The "on" setting used to be "hard," so if you see any references to "hard canonical," it means enabling canonical name redirection. We also used to have a "soft" setting, which some old sites still have. It's useless and if you see it, you should get rid of it!)