IIS Integrated vs Classic Mode

Integrated mode and Classic mode are parts of IIS Pipeline mode. IIS Pipeline mode refers to how a web server processes client requests.

Integrated Mode

It works as a part of IIS 7. It is only available in IIS 7 and above.
It handles all requests through a unified pipeline because of the integration of ASP.NET’s runtime with the Web server.
it uses new and improved services of IIS 7 and above.

Classic Mode

It works as an external plugin with IIS 7. It was the only mode available in IIS 6 and below.
It uses two pipeline modes to handles client requests. One for native code and other for managed code.
It does not use new and improved services of IIS 7 and above.