Formal:
* Est-ce que c'est vous ? (This is the most literal translation and the most formal option.)
* S'agit-il de vous ? (This is a more formal way to ask "Is this you?" and is often used in written French.)
Informal:
* C'est toi ? (This is the most common and informal way to ask "Is this you?")
* C'est bien vous ? (This is slightly less formal than "Est-ce que c'est vous?" and is often used in spoken French.)
Other options:
* C'est toi, non ? (This adds a bit of emphasis to the question and can be used in a casual setting.)
* C'est vraiment toi ? (This is a more surprised way to ask "Is this really you?")
The best way to say "is this you" in French depends on the situation and your relationship with the person you are speaking to.