I can use "Who are you?" when talking to one person.
But what can I use if I'm talking to a group of people?
I can use "Who are you?" when talking to one person.
But what can I use if I'm talking to a group of people?
“Who” can be made plural the usual way, but that is not what is needed here
The “Whos” And “Wheres” Of iOS Device Usage Explained
Source: TechCrunch headline
This is a plural in the sense that it refers to multiple mentions of (or answers to) the question “who?”.
“Who” does not have a plural form like the way that “is” changes to “are”
Generally speaking, the word “who” is a pronoun. It stands in for the mention of a person or people, but has no power to determine in and of itself how many people the speaker is talking about.
“You” does not have a plural form either, but can refer to multiple people
The word “you” in your sentence does not have to change in order to refer to multiple people. To make the reference more clear, you can add “two” or “all” as in “you two” or “you all” (or, regionally, “y'all”).
If you want to ask about the identity of multiple people, convey this with other words
“all” after “who”
Person A: We will need four more chairs set at the dinner table tonight.
Person B: Who all will be joining us?
This construction is informal and mainly AmE.
“all” after “you”
Group A: Trick or treat!
Person B: Who are you all supposed to be?
As indicated above, the contraction “y'all” is employed this way in some regions.
“people”
Group A: Surprise! You win this prize for being the 100th person to cross this new bridge!
Person B: Who are you people?
This construction may be considered brusque.
“they”
Person A: You've never heard of the Kardashians?
Person B: No, who are they?
“They” is usually third person plural but can also be third person singular.
It is the same in the plural:
Who is your best friend?
Who are your best friends?
Who are you? (to one person)
Who are you? (to more than one person) or
Who are you all?
"who" has only one form, but it can refer to plural nouns: Who were the Etruscans? Who are all those people waiting outside?
There is at least one other common possibility that I do not see listed:
Who are all of you?
with "all of you" being synonymous with "you all."
Another example: Where are all of you going to eat?
In short:
There is no plural form for "Wh" questions. They are the same thing whether is singular or plural.
Examples:
Singular: "who are you?"
Plural: "Who are you"?
In this case, people should understand you according to your lookout and body language.
It's just like "What" "HOW", they are not nouns. Singleton or plural form only apply to nouns
Who are you guys?in this example. – Nicolas Raoul Apr 16 '14 at 10:22