The nature of electolytes used in a salt bridge are:
Inert electrolytes
Any electrolyte can be used
Weak electrolytes
Non electrolytes
Inert electrolytes are used as their ions are not involved in any electrochemical change.
Assertion : Salts like KCl,KNO3 i.e., inert electrolytes are used in salt bridge.
Reason : An inert electrolyte can easily be filled in the U-tube.