IANAifType-MIB: View SNMP OID List / Download MIB
Download standard MIB format if you are planning to load a MIB file into some system (OS, Zabbix, PRTG ...) or view it with a MIB browser. CSV is more suitable for analyzing and viewing OID' and other MIB objects in excel. JSON and YAML formats are usually used in programing even though some systems can use MIB in YAML format (like Logstash).
This MIB module defines the IANAifType Textual Convention, and thus the enumerated values of the ifType object defined in MIB-II's ifTable.