Formal:
* Où êtes-vous ? (oo eh-tay voo?) - This is the most formal way to ask. It's used for someone you don't know well or in a formal setting.
Informal:
* Où es-tu ? (oo eh-too?) - This is the informal way to ask, used for friends and family.
* Tu es où ? (too eh oo?) - This is a more casual and common way to ask among friends.
Other options:
* Où vous trouvez-vous ? (oo voo troo-vay voo?) - This is another formal way to ask, meaning "Where do you find yourself?".
* Vous êtes à quel endroit ? (voo eh-tay ah kel on-droo?) - This literally translates to "Where are you located?".
Remember that the best way to ask depends on who you are talking to and the level of formality of the situation.