When should I select a “Classic” project and when should I select a “Gateway” project?

You are using our current interface per XML and are asked by your (shop) system for the API key / configuration key? Please select the Gateway project in this case.

You are using our interface per name-value-pair (NVP) via HTTP GET and you need a project / notification password? Please select the Classic project in this case.

The project type can be selected as follows:
Log in to your merchant account. Click “New project” in the left menu. Select the desired product for which you want to add a project. Select the desired project type in the following graphic.