The 51Degrees .NET Detector is designed to be quick to deploy for even low skill developers, and provide fast, accurate and consistent results for both real time device detection within web sites and offline analysis. All the source code and 51Degrees free Lite data is licenced under the Mozilla Public Licence version 2.

The Detection solution is a single project for .NET 3.5 and up, distributed as C# source code and as a DLL. .NET 2 is no longer supported.

The following pages explain where to download official distributions, initial deployment, obtaining updates to device data before covering more advanced features such as logging and advanced redirection methods. For documentation about Framework, the 51Degrees mobile site optimiser for .NET, see the Framework Documentation.


  • .NET Prerequisites

    A list of the environment that is needed to run the .NET solution along with configurations that have been tested.
  • Getting Started

    Explains how to use 51Degrees device detection with .NET 3.5 and above. Installation methods cover NuGet and adding assemblies to projects manually including both web and offline analysis applications.
  • Upgrade V2 Web Sites to V3

    Explains the major differences between version 2 and 3 before guiding through the upgrade process for both Lite and Premium device data users.
  • Operational Summary

    A brief overview of the methods used to perform device detection under .NET using the HTTP header User-Agent including overriding of HttpBrowserCapabilities and registering the HttpModule.
  • Distributions

    Page describes the ways you can download 51Degrees device detection for .NET.
  • Data Updates

    Page provides detailed instructions about using 51Degrees license keys and configuring automatic updates for Detector projects.
  • Constants

    List of constants that can be used to alter the behaviour of Foundation for your specific requirements.
  • Web Applications

    Page outlines the use of 51Degrees Detector in a .NET web project or just about any .NET CMS.
  • Image Optimiser

    Append the required image size in pixels to an image URL and have 51Degrees return a precisely sized image. Go further with the "auto" parameter to automatically serve precisely sized images.
  • Passing Properties To Client Side

    An optional include script that can be added to the web page to provide information to client side javascript concerning the device enabling decisions to be taken in javascript.
  • Client Side Overrides

    Uses javascript to interrogate the device for additional information. Useful in situations when a specific model of a phone, such as iPhone or iPad is required due to user agent strings used in Apple mobile devices not allowing to distinguish between the device type and model on its own.
  • User Performance Monitoring

    Explains how to implement web site performance monitoring into normal web page processing without the need for separate monitoring scripts.
  • Offline Applications

    51Degrees device detection can also be used in offline applications such as log file parsing and analysis. Page provides basic set up information and a step-by-step example of adding the 51Degrees DLL to a C# project and example code.
  • SQL Server

    51Degrees device detection functionality can be used within SQL Server to add extra properties to user agent fields. Deployed as an assembly functions can be called to returned individual properties, or tables of properties.
  • IIS Modification

    IIS Modification to improve website performance. Topics covered are caching and compression within IIS and Fixing the Vary Header.
  • Log Troubleshooting

    Table containing all possible error messages that 51Degrees Detector can produce with relevant descriptions and solutions (if available).
  • Reference

    MSDN style, comprehensive .NET documentation for 51Degrees Detector.
  • Native Code

    Example of accessing native code from .NET.
  • Examples And Questions

    Page containing examples of using 51Degrees .NET device detector.