If you book an RV site, most of them will accommodate a tent as well as the RV. I don't think you can do a tent with the cabin rentals though.
It depends in what your booking, they have several different sites
Either or $$
Cabin
You need to decide it is either a cabin rental or a campsite where you can get just a tent site or sites for traikers/RV and tents.
The have both tent sites an rv sites
If you don't want to sleep in a tent or your RV you need to ask for a cabin. I have never seen any tents just RVs
I am assuming by asking about "Campsites" you are referring to how the resort is identified on the Disney reservation system. They differentiate between The Campsites at Disney's Fort Wilderness Resort, and The Cabins at Disney's Fort Wilderness Resort, which is a Moderate level resort in the system. If you book a reservation at The Campsites at Disney's Fort Wilderness Resort you are NOT booking a cabin. You are booking a site to place either a tent or an RV on. If you don't own or intend to rent an RV, then yes you will need to bring a tent to sleep in.
They have many different sites they do have tent sites
They have tent sites, camper/trailer sites and cabins. So all of the above.
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