A mattress that has open coils is an innerspring mattress, no matter how many layers of foam are on top of the support core. A hybrid always has pocketed coils. Don’t be fooled by marketing gimmicks that try to pass off innerspring mattresses as hybrids because they have a foam Euro top or pillow top. If it doesn’t have pocketed coils, it is not a hybrid.
Another thing to watch out for is the comfort layer. A hybrid always has at least two inches of foam in the comfort layer. A pillow top sits on top of the comfort layer. It provides extra padding, but it is not a comfort layer.
So take a look at the construction of any mattress you’re considering. If it has less than two inches of foam or a comfort layer made of something other than foam, it isn’t a hybrid.