For a long time it was aftermarket HID kits. Installing those was a bit of a pain because of the separate ballasts and associated wiring. They were blinding because the projectors required a cut off and most were installed in halogen housings.

Now most people are installing aftermarket LED kits. For the most part those are less blinding. I upgraded our old Impreza with some but chose the lowest lumen numbers I could find and they are also engineered to emit light in the same locations and angles that the halogen ones did. I did some tests with the garage door and standing in front of it where a car would be and it's non-blinding for oncoming traffic.