Spoiled onions may develop dark spots, which will eventually begin to grow mold. You'll also want to avoid onions that have started sprouting, as this indicates they're beginning to go bad. You can also feel your onions to check how fresh they are. Onions with soft or mushy spots are starting to go bad.

How long does it take for onions to go bad?

Fresh whole onions can last for up to 6 weeks but can keep for up 2 months if stored in the fridge. If refrigerated, fresh chopped onions can last in the fridge for 1 week. Onions can last for up to 8 months in the freezer. Whole raw onions will last for up to 6 weeks in a cool, dark area.

What does bad onion smell like?

Rotten, or spoiled, onions will have a noticeably 'off' aroma, much like rotting compost. The sweet hint of caramelisation will be gone, in its place will be a sour decaying smell. This smell is unavoidable and breath-takingly pungent.