Dijon mustard and any other mustard does not need to be refrigerated.
Mustard does not have to be refrigerated although it is okay to refrigerate the mustard if you desire.
But mustard and even ketchup and most other condiments can be left out safely at room temperature including mayonnaise.
Ketchup does expire and as the ketchup gets old it begins to harden and clump up and might smell bad.
However as long as the expired ketchup smells okay then it's safe to eat although it may not taste as good.
You do not have to refrigerate ketchup as ketchup is just basically tomatoes and nothing in ketchup will cause it to spoil at room temperature.
As long as the ketchup is kept sealed when not in use then it can remain safe at room temperature without refrigerated for a long time.
Ketchup is not refrigerated in restaurants because ketchup is safe at room temperature and ketchup is being used constantly as well in the restaurant.
Ketchup can be refrigerated but ketchup can be left out at room temperature without worry about it spoiling.
Ketchup does not require refrigeration so you can safely leave ketchup out at room temperature.
You should keep ketchup in the fridge if you want too but it's not required.
Ideally you should keep ketchup at room temperature such as on the table, counter, in the pantry etc as it requires no refrigeration.
Ketchup should be kept in the cupboard or pantry or on the counter or table at room temperature.
Keeping ketchup in the refrigerator is just a waste of space in the refrigerator because ketchup does not require refrigeration.
You don't need to or have to refrigerate Ketchup.
Ketchup can safely be left out at room temperature.
You can refrigerate ketchup but there's no need to as the Ketchup won't spoil or go bad at room temperature.
Most condiments like Ketchup don't require refrigeration.
Ketchup does not need refrigeration and will keep for 6 months or even longer out at room temperature after opening it.
You can refrigerate the opened bottles of ketchup to keep them fresher longer but you do not have to refrigerate ketchup for it to keep.
Ketchup is basically just tomatoes made into the ketchup and as long as you keep the ketchup bottle closed when not using it the ketchup will last for a long time.
I never refrigerate my ketchup and a lot of restaurants do not refrigerate their ketchup either.
Of course the ketchup in restaurants is used up pretty quickly but there's still no need to refrigerate ketchup unless you want too.