Is it from who or from whom?

From whom (not “from who”) is the correct choice at the beginning of a question (e.g., “From whom did you get it?”).

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 “from” at the end (e.g., “Who did you get it from?”).

“From whom” (not “from who”) is also the grammatically correct choice at the beginning of an adjective clause (e.g., “His colleague, from whom he learned so much, retired last year”). But again, “who” is often the better option, with “from” in a later position (e.g., “His colleague, who he learned so much from, retired last year”).

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