Server-Side Includes (SSI) are a type of HTML comment that directs the web server to dynamically generate data for the webpage whenever a data input is requested.

With no programming or CGI scripts, Server-Side Includes, when applied to an HTML document, provide interactive, real-time features, such as

  • Echoing current time, conditional execution based on logical comparisons
  • Querying or updating a database
  • Sending an email

An SSI consists of a special sequence of characters, called tokens, on an HTML page. As the page is sent from the HTTP server to the requesting client, the server scans the page for these special tokens. When a token is found, the server interprets the data in the token and performs an action based on the token data.