This is a post about which chestnuts you can eat and which ones you cannot eat.To tell the difference between an edible chestnut (from Castanea Sativa) and a non-edible chestnut (Horse Chestnut or Buckeye) you need to take a close look at the pod that the chestnuts grow in. Once the chestnut (seeds) are out of their pods they can look very similar to each other.
The pod of the edible sweet chestnut has a sort of "porcupine" look to it with thin prickly spikes that point out in all directions and form a sort of thicket where you cannot see anything but the spikes. These are green while the chestnuts are forming and then turn brown when the chestnuts are mature. Handling these pods without gloves can be quite tricky.
The chestnuts from a Horse Chestnut or Buckeye on the other hand have short bumpy spikes on a smooth ball shaped fruit where you can see the surface between the spikes. As you can see in these images there are a lot fewer spikes which are also shorter and less pointy than those of the edible chestnuts.
The leaves are also very different. Those of the Horse Chestnut and Buckey are palmate with five leaflets like the one in the image below.