NuGet packageOwin.Framework.StaticFiles
GitHub sourceOwinFramework.StaticFiles

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Responds to requests by returning the contents of files in the file system. Supports directory mapping, security and file extension restrictions

This middleware will serve static files from your web site. Static files are where you have a one-one mapping between URLs on your web site and files on disk. You can configure the location on your file system where the files reside and the URL on your site where these files can be downloaded from.

You can limit the files that are served by file extension and restrict access to files using any Authorization middleware that supports the OWIN Framework.

You can configure multiple static file middleware components in your owin pipeline to serve files from different locations with different configurations.

You can configure static file caching. For this to work you will need to add some output caching middleware to your Owin pipeline.


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).

For supported configuration options see the StaticFilesConfiguration.cs file in this folder. This middleware is also self documenting, and can produce configuration documentation from within.

The default configuration will serve files from an assets folder in your web site via urls starting with /assets. For example if you place an image called logo.png in the assets folder of your site, then you can retrieve this file from http://mydomain/assets/logo.png.

This is an example configurations that assumes you use Urchin for as your configuration mechanism.

Example of configuring the OWIN Framework builder to specify the path to the middleware configuration. This example configures two instances of the static files middleware called "Public resources" and "Protected resources" that are configured at "/middleware/staticFiles/public" and "/middleware/staticFiles/public" respectively:

    .As("Public resources")
    .ConfigureWith(config, "/middleware/staticFiles/public");

    .As("Protected resources")
    .ConfigureWith(config, "/middleware/staticFiles/protected");

This is an example Urchin configuration that will work with the code above:

    "middleware": {
        "staticFiles": {
            "public": {
                "staticFilesRootUrl": "/assets/public",
                "documentationRootUrl": "/config/assets/public",
                "rootDirectory": "~\\assets",
                "enabled": "true",
                "includeSubFolders": "true",
                "FileExtensions": [
                    { "extension": ".html", "mimeType": "text/html" },
                    { "extension": ".css", "mimeType": "text/css" },
                    { "extension": ".js", "mimeType": "application/javascript" },
                    { "extension": ".jpg", "mimeType": "image/jpeg" },
                    { "extension": ".jpeg", "mimeType": "image/jpeg" }
                "maximumFileSizeToCache": 10000,
                "totalCacheSize": 1000000,
                "maximumCacheTime": "00:30:00",
                "requiredPermission": ""
            "protected": {
                "staticFilesRootUrl": "/assets/protected",
                "documentationRootUrl": "/config/assets/protected",
                "rootDirectory": "D:\\assets",
                "enabled": "true",
                "includeSubFolders": "true",
                "FileExtensions": [
                    { "extension": ".html", "mimeType": "text/html" }
                "maximumFileSizeToCache": 10000,
                "totalCacheSize": 1000000,
                "maximumCacheTime": "00:30:00",
                "requiredPermission": "user"

This configuration specifies that:

  • The url http://mysite/assets/public is mapped to the files in the \assets sub-folder beneath the root folder of the web site. It also specified that the configuration of this middleware can examined by retreieving the url http://mysite/config/assets/public.
  • The url http://mysite/assets/protected is mapped to the files in the absolute file path D:\\assets. It also specified that the configuration of this middleware can examined by retreieving the url http://mysite/config/assets/protected.
  • For the protected assets this configuration also specifies that the request must be made in the context of a user with the user permission. This required permission relies on having some authorization middleware installed and configured on the same route. If there is no authorization middleware confgured then the required permission will not be enforced.
  • All static files are cached in memory for 30 minutes if they are less than 10,000 bytes in size up to a maximum total memory consumption of 1,000,000 bytes for all files. This featre relies on output caching middleware. If there is no output caching middleware configured in your OWIN pipeline then static files will not be cached.

Output caching

You will frequently want to use the Static Files middleware in conjunction with the Output Cache middleware because static files by definition do not change and can be cached.

When this Static Files middleware and any implementation of output caching are both configured on the same route they will work together to produce the correct behavior - for example if the static file is updated then the Static Files middleware will tell the output cache to flush it from the cache.

The output cache middleware is configured using categories and priorities. The category indicates the type if content and priority is a reflection of how expensive it is to fetch the data from backing store and therefore how beneficial it is to cache the data.

For now when this Static Files middleware returns this information to the output cache it will either send back "SmallStaticFile" or "LargeStaticFile" as the category and "High" or "Never" as the cache priority. You should use these names when configuring the output cache. In a future version of the Static Files middleware these things should be made configurable.

This Static Files middleware has a maximumFileSizeToCache configuration option. Files over this size will be categorized as "LargeStaticFile" and files under this size will be categorized as "SmallStaticFile".