This post is the first of a two part series about handlers and modules and is an attempt to offload what I know about handlers to you. Knowing what handlers are and how they work is what separates the savvy from the not-so-savvy when it comes to IIS administration. Although very few modules in the DotNetNuke ecosystem use/rely on handlers, those that do experience a steady stream of support calls along the lines of “hey, XYZ doesn’t work” and it is down to a handler issue. Examples of modules that use handlers are Ultra Video Gallery and Document Exchange. DotNetNuke uses handlers itself as well. So what is a handler? In a nutshell a handler is piece of code that handles a web request. To understand why it’s good to know more about this you need to look closer at http traffic (i.e. the bits and bytes that go back and forth between your browser and the server).