Internet Server API

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What Does Internet Server API Mean?

An Internet server API (ISAPI) is a set of ready-made Windows program calls that developers and programmers can use in order create custom enhancements or extensions to ISAPI-compliant HTTP servers or web servers. These enhancements are called Internet Server Extension Applications (ISA) and ISAPI filters, which provide functionalities such as database invocation and even for building Web pages dynamically for a Web client (browser) to display.


Techopedia Explains Internet Server API

The Internet Server Application Programming Interface makes it easier to write database applications like an entry system for order forms or for a custom catalog. With ISAPI, a programmer can collect information from a user through an HTML form and then return a page which has been customized for that user.

ISAPI enables a programmer to write two types of extensions for a server:

  • Internet server applications (ISA), which provide similar functionalities to CGI applications but are considered faster since they are in the form of dynamic link libraries (DLL), which are loaded into memory and do not need to be located and then read again like CGI applications, which are considered as executable.
  • ISAPI filters, which are used by a web server to assist in various events in the course of processing a given HTTP request like reading and writing data or even outputting of log entries. ISAPI filters can add other functionalities to a server like:
    • Compression
    • Encryption
    • Custom authentication
    • Logging schemes

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Margaret Rouse
Technology Expert
Margaret Rouse
Technology Expert

Margaret is an award-winning technical writer and teacher known for her ability to explain complex technical subjects to a non-technical business audience. Over the past twenty years, her IT definitions have been published by Que in an encyclopedia of technology terms and cited in articles by the New York Times, Time Magazine, USA Today, ZDNet, PC Magazine, and Discovery Magazine. She joined Techopedia in 2011. Margaret's idea of a fun day is helping IT and business professionals learn to speak each other’s highly specialized languages.