Here you look up any field of an e-invoice. The field browser shows all 1,274 fields: 311 from the EN 16931 core and 963 from the EXTENDED profile of ZUGFeRD and Factur-X, 17 of which carry an ordinary BT or BG number. Search by an identifier such as BT-1 or by a term, and filter by field kind and scope.

When you expand a row, you see everything the standard defines for that field: the description, the usage note, how often the field may occur (cardinality), the data type, the path in the XML for CII and UBL, and the validation rules, grouped by rule set.

The field browser is part of the Technical Details add-on for the eInvoice Viewer, a paid product. Together with the viewer, the same details also appear right at the field of the open invoice. It shows the fields of the EXTENDED profile together with the Extended Profiles add-on.