Stockholm is full of 'fake' taxis that take you longer routes and charge you more money. I'd much rather use Uber.
Regular, real/official, taxi's are easily recognisable by their number plate which is orange with black letters whereas regular vehicles are white with black letters. You don't have to use fake taxi's, that's your choice. A regular taxi ride in Stockholm and a Uber ride (depending on the time of day) usually don't have a big price difference between them. Unless you want to take one of the Tesla taxi's.
My brother lives there and explained to me how they can be identified, I otherwise would not have known.