I want to buy a pair of polarized sunglasses, but there are so many fake polaride sunglasses in the market nowadays, they almost have the same view when you wear ordinary sunglasses, how can I identify them if I don't have a special test paper?

So, do you have a cellphone, put the sunglasses on, look at the screen of your phone from different angle, if you always see black and bright vision of the screen, that's mean it is a real one.