The default file that gets shown when for a directory on a web server, usually index.html
The directory index is the default file that is served when URL for the directory is requested. The directory index file is usually index.html. So for example when a client requests http://example.com/, the server will show the contents of index.html from the appropriate directory for that site.
index.html is the most common file name, but web servers come configured with a variety of defaults:
index.htmindex.phpindex.aspxdefault.htmlhome.html
Most servers can be configured to use one of a list of possible default files. On Apache for example:
DirectoryIndex index.php index.html
Would instruct the server to use index.php first if it is available and then to check for index.html.
If no directory index file is present, servers may either show a directory-listing or a 403-forbidden error.
