Editing Web server (section)

==== URL mapping ====
{{Update section|date=June 2023}}{{Main|URL mapping}}<blockquote>"URL mapping is the process by which a URL is analyzed to figure out what resource it is referring to, so that that resource can be returned to the requesting client. This process is performed with every request that is made to a web server, with some of the requests being served with a file, such as an HTML document, or a gif image, others with the results of running a CGI program, and others by some other process, such as a built-in module handler, a PHP document, or a Java servlet."<ref name="ws-url-mapping">{{Cite web|url=http://people.apache.org/~jim/ApacheCons/ApacheCon2002/pdf/Bowen-urlmap-ACUS02/bowen-urlmap-ACUS02.pdf|title=URL Mapping|author=R. Bowen|publisher=Apache software foundation|date=2002-09-29|access-date=2021-11-15|language=en|archive-date=15 November 2021|archive-url=https://web.archive.org/web/20211115181448/http://people.apache.org/~jim/ApacheCons/ApacheCon2002/pdf/Bowen-urlmap-ACUS02/bowen-urlmap-ACUS02.pdf|url-status=live}}</ref>{{Update inline|date=June 2023}}</blockquote>In practice, web server programs that implement advanced features, beyond the simple ''static content serving'' (e.g. URL rewrite engine, dynamic content serving), usually have to figure out how that URL has to be handled, e.g. as a:
* [[#URL redirection|URL redirection]], a redirection to another URL;
* ''static request'' of [[Computer file|file]] content;
* ''dynamic request'' of:
** [[Directory (computing)|directory]] listing of files or other sub-directories contained in that directory;
** other types of dynamic request in order to identify the program / module processor able to handle that kind of URL path and to pass to it other [[URL parts]], i.e. usually path-info and [[query string]] variables.

One or more configuration files of web server may specify the mapping of parts of '''URL path''' (e.g. initial parts of [[Path (computing)|file path]], [[filename extension]] and other path components) to a specific URL handler (file, directory, external program or internal module).<ref name="ws-static-rqs-root-dir">{{Cite web|url=https://httpd.apache.org/docs/2.4/urlmapping.html|title=Mapping URLs to Filesystem Locations|publisher=Apache: HTTPd server project|year=2021|access-date=2021-10-19|language=en|archive-date=20 October 2021|archive-url=https://web.archive.org/web/20211020053640/http://httpd.apache.org/docs/2.4/urlmapping.html|url-status=live}}</ref>

When a web server implements one or more of the above-mentioned advanced features then the path part of a valid URL may not always match an existing file system path under website directory tree (a file or a directory in [[file system]]) because it can refer to a virtual name of an internal or external module processor for dynamic requests.