Is it for who or for whom?

For whom (not “for who”) is the correct choice at the beginning of a question (e.g., “For whom is this delivery?”).

But “whom” has a very formal stylistic effect, which you may want to avoid, so in most everyday contexts it is better to use “who” and put the preposition “for” at the end (e.g., “Who is this delivery for?”).

“For whom” (not “for who”) is also the grammatically correct choice at the beginning of an adjective clause (e.g., “The teacher, for whom he was supposed to be substituting, was in her classroom”). But again, “who” is often the better option, with “for” in a later position (e.g., “The teacher, who he was supposed to be substituting for, was in her classroom”).

The QuillBot Grammar Checker can help ensure you’re using “who” and “whom” correctly.