How do you adjust headlights on a 2016? Asking for a friend

There is an alignment procedure in the Repair Manual (more info), under Vehicle Exterior: Lighting (Ext): Headlight Assembly: Adjustment. No special tools are required, just a way to measure distances and make markings on a wall, either 25 feet or 3 meters in front of the car.

Before making adjustments, I’d suggest checking that both headlight assemblies are operating properly. There aren’t separate lamps for high and low beams, just a mechanical shade that moves out of the way when high beams are selected. If the shade or its control wiring has failed on one side, it could cause the effect you describe, with one side bright and the other dim.

 

My recollection (from earlier Prius generations) is that reaching down to the adjuster requires a Phillips screwdriver, which maybe isn't a very 'special' tool, but needs to be long enough. (My usual go-to screwdriver is a ratchet handle with a long shaft and swappable bits, but that shaft is to wide to go in there. I bought a long plain Phillips screwdriver just for the purpose.)