defaultDocument

In computing, defaultDocument refers to a configuration setting that determines which resource should be served when a URL targets a directory rather than a specific file. Its purpose is to provide a predictable landing page for directory requests and to improve user experience and SEO by avoiding directory listings.

Different web servers implement the concept with their own terminology and syntax. Apache uses the DirectoryIndex directive to specify a prioritized list of filenames (for example index.html, index.htm, default.html) that are tried in order when a directory is requested. Nginx uses the index directive to define the default index file(s) for a location. Microsoft IIS exposes this as the Default Document feature, configured in web.config as a list of filenames to check such as index.html or default.aspx.

Operational behavior: if one of the configured filenames exists in the requested directory, it is returned with a 200 status. If none are found, server behavior depends on configuration and may include serving a directory listing, returning a 403 Forbidden, or delegating to a custom error page. The setting can be affected by file system case sensitivity, virtual paths, and security restrictions.

Notes: Many frameworks expose similar functionality under names such as DefaultFiles, DefaultDocuments, or defaultDocument, often integrated with routing or static file middleware. Properly configuring a default document can reduce broken links, prevent exposed directory structures, and improve load speed by avoiding unnecessary redirect loops.