The third version of Fortnox API is organized around REST. This means that we’ve designed it to have resource-oriented URLs and be as predictible as possible for you as developer.

It also means that we use HTTP status codes when something goes wrong and HTTP verbs understod by many API clients around the web.

We use a modified version of OAuth2 for authentication to offer a secure way for both you and our users to interact.

The API is built to support both XML and JSON, but for the most part the .NET SDK is used in a .NET environment that uses XML. In this documentation all the examples will be in either JSON or using our .NET SDK.

We encourage you to read all the articles in the general section first, before going forward and learning about the different resources. This to ensure you get an understanding of some of the shared components of the API such as parameters and error handling.

We strive to have working code examples for every request in the documentation, but we also have more documented code example for PHP and Ruby.

To get started with the .NET SDK we encourage you to read the quick start guide.