51Degrees API Documentation  4.3Newer Version 4.4



An aspect of a web request is a specific entity that is involved in that request. Some examples of aspects are:

  • The device hardware being used to make the request.
  • The operating system running on that device.
  • The physical location of the device.
  • The ISP that is being used to service the request.
  • The cell tower that services the request (If the device is a mobile using its network data access)
  • etc

Each aspect can have one or more associated properties. For example, the device hardware aspect has properties such as:

  • Type of device (smart phone, computer, smart TV, games console, etc)
  • Screen size in pixels
  • Screen size in inches
  • etc

Cloud Service

A service accessed via a web request. It is used to send data, receive data, carry out processing, or all of the above.

A cloud service can be used in much the same way as a local service running on the same machine, with the extra step of a web request being required.

Data Tier


The 51Degrees Distributor is a cloud-based web service that distributes data files for 51Degrees services. In order to access it, you will need to have a license key that defines the products that you are allowed to access.

Native Code

Native code refers to code written in C/C++. This is done to maximize performance, as many more optimizations can be made in lower level languages than compared to high level languages such as C# or Java.

Resource Key

A resource key is used by the 51Degrees cloud service as a shorthand for various parameters that can be sent as part of a request. For example, the properties that the user wishes to be populated in the response and any license keys that allow access to more properties or a greater request allowance.

Web Request

A web request is a message sent from a client device to a server where a web site is hosted. This message will usually be a simple request for a particular web page or other resource. However, it also contains a lot of additional information (evidence) that can be used to infer details about different contexts within which the request takes place (aspects).

Web Server

A network connected machine designed to serve content to external devices, or carry out tasks. Most commonly, a web server is the host of a website.