Same resource

Two or more resources can be the same resource even though the URLs for them are different. This can be due to URL resolving, server settings, redirects, or DNS aliasing.

If the resolved URLs for two resources are identical, the resources are the same resource.

Depending on the server, URLs can either be case-sensitive or case-insensitive, meaning that the links <a href="page1.html"> and <a href="Page1.html"> may lead to either the same or two different pages.

Fully resolved URLs can be different, but still lead to the same resource after making the HTTP request, due to redirects and DNS aliasing. For example, these URLs are all fully normalized:,, but the server can nonetheless be configured to serve the same site for http:// and https://, and the same site for and This is common, but not guaranteed.

Some types of redirects are also caused by user agents, e.g. ensuring that and resolve to the same resource independently of the presence of a trailing /.