In many web servers, including Apache, the file index.html is served by default if a URL is requested that corresponds to a directory on the server. In particular, the shortest URL for a web site, http://domain.example/, is by default served by these web servers from a file called "index.html".

Other web servers have different defaults, for example "index.htm" or "default.htm". Modern web servers can typically be configured to serve any file or run any server-side script in response to any given URL, but "index.html" remains the most popular file name.