To tell if potatoes are bad, look for the following signs:

• Texture: Raw potatoes should be firm and not soft or mushy. If they feel squishy or have shriveled, wrinkled skin, they are likely spoiled and should be discarded

• Skin appearance: Check for large bruises, dark or black spots, and blemishes on the skin. These can indicate rot or spoilage

• Odor: Fresh potatoes have an earthy or nutty smell. A musty, moldy, or foul odor is a clear sign of spoilage

• Sprouts: Small sprouts can be removed and the potato still eaten safely, but extensive sprouting signals the potato is past its prime. Avoid eating the sprouts themselves as they contain toxic compounds

• Green coloration: Green patches indicate solanine, a toxin. Cut away green parts before cooking or discard if extensive

• Cooked potatoes: These should be eaten within 4 days. If they develop mold or a strong odor, discard immediately as they can harbor harmful bacteria even without visible signs

In summary, discard potatoes that are soft, mushy, have dark spots, a bad smell, mold, or extensive sprouts. Small sprouts can be removed, but green parts should be cut off to avoid toxins