If you are using title case (as opposed to sentence case), then yes, you needs to be capitalized. In title case, only so-called minor words are lowercased: articles, (short) prepositions, and conjunctions. You however is a pronoun, which belongs to the major words, along with nouns, verbs, adjectives, and adverbs. Consequently, the word you must be capitalized in titles and headings:
Wish You Were Here
Are You Afraid of the Dark?
Who Do You Think You Are
Convert your titles automatically using the Title Case Converter to get a better understanding which words are capitalized in title case, and which are not.
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