NuGet packageOwin.Framework.NotFound
GitHub sourceOwinFramework.NotFound

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Returns a 404 (not found) response when no other middleware handled the request

This middleware will return a 404 response always. It will place itself after all other middleware in the pipeline so that when no other middleware handled the request a 404 response will be returned to the client.

If you want this behaviour only on certain routes through the OWIN pipeline then you can configure this middleware only on those routes. You can also add multiple instances of this middleware to the OWIN pipeline to have different 404 templates for different routes. For example if you have an API that returns JSON, you might want the API to also return JSON in the 404 case.


The OWIN Framework supports any configuration mechanism you choose. At the time of writing it comes bundled with support for Urchin and web.config configuration, but the IConfiguration interface is trivial to implement.

With the OWIN Framework the application developer chooses where in the configuration structure each middleware will read its configuration from (this is so that you can have more than one of the same middleware in your pipeline with different configurations).

This middleware has very few configuration options. See the NotFoundConfiguration.cs for details.

This is an example of adding the not found middleware to the OWIN Framework pipeline builder.

    .As("Not found")
    .ConfigureWith(config, "/middleware/notFound");

If you uses the above code, and you use Urchin for configuration management then your configuration file can be set up like this:

    "middleware": {
        "notFound": {
            "template": "\\templates\\404.html"