What is the difference between 'Single Value' and 'Several Values' when setting up custom parameters?

When configuring custom parameters ("Mapp Q3 > Custom Parameters"), you can set the number of parameter values. This determines whether you want to submit a single or multiple information simultaneously.

Both allow sending a list of information in a tracking request. However, only multi-value parameters can be logically connected. This means that the individual pieces of information can be directly linked to each other based on their position within the request.

In this example, the parameter "error message" and the parameter "error message code" belong together and should therefore also be directly linked in the evaluation:

So, if you want to track several parameters with different information in one request, which you want to link together, you should use the multi-value parameters.

You will find additional information and examples on this page:  What are multi-value parameters and how are they working?