Apache HTTP Server is an open sourceHTTPweb server for Unix platforms (BSD, Linux, and UNIX systems), Microsoft Windows, and other platforms. The author claims the name was initially chosen as a catchy name in order to be original, but the most widespread interpretation (which almost immediately surfaced) is that the name comes from the fact that when it was developed in early 1995, it consisted of changes in the code to the most popular HTTP server of the time, NCSA HTTPd 1.3 and was therefore "a patchy" server. It would later be rewritten from scratch and no longer contains any NCSA code.
Apache features highly configurable error messages, DBMS-based authentication databases, and content negotiation but has been criticized for its lack of GUI tools to aid in its configuration.
Initially, Apache was the only viable open source alternative to the Netscape web server (nowadays known as iPlanet). It has since evolved to rival (and probably surpass) almost any other Unix based HTTP server in terms of functionality and speed. Since April 1996 Apache has been the most popular HTTP server on the Internet; in May 1999 it was running on 57% of all web servers. In May 2003 this percentage increased to 62%.
The Apache HTTP Server is developed and maintained by an open community of developers under the auspices of the Apache Software Foundation.
Apache has other powerful features included in a large set of modules, including mod_perl, many authentication modules (mod_access, mod_auth, mod_digest to name a few) as well as a web proxy module and an extremely useful URL rewriter (also known as a rewrite engine) called mod_rewrite. Apache logs can be analysed through a web browser using free scripts such as awstats.
Apache is the web server component of the development methodology called LAMP.