In Web pages, directives embedded in HTML comments that are intended to be interpreted by the Web server.

(SSI) Content that sits outside an HTML file that is dynamically included by the Webserver upon page request. For example, a user requests a page, index.shtml. The Webserver is configured to handle files with the extension *.shtml differently than files with a normal *.html extension. For files with a normal *.html extension, the Webserver retrieves the file from the file-system and returns to the user's browser for rendering and display. For files with a *.shtml extension, the Web server fetches the file from the filesystem, and, before returning to the end user, reads the file and looks for special directives of the form For each directive found, the Webserver will either (a) take the a file from a specified file system location, open it, and insert it into the Web page before sending it to the end user or (b) execute a script on the server and take the results of the script and insert them into the Web page before sending it to the end user. Server-side includes are used to make content modular so that (a) one content component can be included on multiple Web pages and (b) content components can be changed in one place and automatically be reflected in all Web pages.

A facility for including dynamic information in documents sent to clients, such as current date, the file's last modification date, and the size or last modification of other files.