Content Negotiation Headers


This guide is for the deprecated Flex.API. Please don't use it for new implementations.

See Integration Options, and feel welcome to ask our friendly help desk.

The data format is determined by the HTTP request headers Content-Type, Accept, Accept-Charset, and Accept-Language.

These are the headers to send and receive JSON:

Request Headers
Content-Type: application/json; charset=utf-8;
Accept: application/json;
Accept-Charset: utf-8
Accept-Language: de_DE

The Content-Type header is only needed in POST or PUT requests, since the body is not evaluated in a GET request.

The request is expected in UTF-8, and also the response uses this encoding. The charset header is optional.

The Accept-Language does not influence the payment window but the API response, for instance error messages. It can be set to de_DE or en_US. The language header is optional, German is the default.