A web server (sometimes called an HTTP server or application server) is a program that serves content using the HTTP protocol. This content is frequently in the form of HTML documents, images, and other web resources, but can include any type of file. The content served by the web server can be pre-existing (static content) or generated on the fly (dynamic content).

In order to be considered a web server, an application must implement the HTTP protocol. Applications built on top of web servers (such as blogging software, forums, or wikis) belong in the separate web software category.