Can I use my Iphone 5 case on my iphone 5s?

I want to buy an Otterbox Defender case for my Iphone 5s of of Amazon and not the actual website. I can't find the Iphone 5s case anywhere but the Otterbox website. Is there even a difference between my old iphone 5 case and the new 5s case I want? Should I even but another case or use my old one?

Yes you sure can

They're the same size, so yeah you can still use your old case if you want/