API Versions
The API can be called in two versions. Version 1 references the way it was from day 1 of the API. Version 2 denominates the protocol version introduced in summer 2015. The vast majority of commands of the API does not differ in both versions and is available in both versions. The main difference of the two API versions is in the area of authentication and auth-session management which is more robust and secure in v2. Future extensions of the API may require a higher (than v1) protocol version. If not stated otherwise, the commands in this document are available in both API versions.
Information: The name "version 2" suggests that this version is "newer" or "better", it is not. It is simply different. So it is absolutely fine to use version 1. The default user interface, the Excel Client and many other systems rely on and use version 1 authentication.