In web applications that use OWIN the application developer must configure an OWIN pipeline. Requests received by the web server are pushed through the pipeline until a middleware chooses to handle the request. Downstream middleware refers to middleware that is positioned further down the pipeline than the current one, and will be given an opportunity to handle the request later than the currently executing one.

There is a downstream communication mechanism in the OWIN Framework that allows a middleware to pass information to middleware that is downstream, i.e. further down the pipeline.