harry potter - Which name would have appeared on the Marauder's Map for Lord Voldemort?

Lord Voldemort is known to most of the wizarding world as "Lord Voldemort."

Would he have been named this on the Marauder's Map or would he have been called "Tom Riddle"?

Answer

Film logic

The map in the film appears to shows the person's chosen name, not their given name. That's why Newton Scamander's name shows up as Newt.

Presumably "Lord Voldemort" would show up with that name, rather than "Tom Riddle."

Book logic

The map in the book appears to shows the person's given name, not their chosen name. In Harry Potter and the Goblet of Fire, Harry spies "Bartemius Crouch" in Moody's rooms. Had it been using Barty Crouch's preferred name, it presumably would have shown up as "Barty Crouch".

Presumably "Tom Riddle" would show up with that name, rather than "Lord Voldemort".

Peeves was not the only thing that was moving. A single dot was flitting around a room in the bottom left-hand corner – Snape’s office. But the dot wasn’t labelled ‘Severus Snape’ … it was Bartemius Crouch.

_{^{Harry Potter and the Goblet of Fire: CHAPTER TWENTY-FIVE — The Egg and the Eye}}