Preposition + who (whom)

When a pronoun follows a preposition (to, with, from, for, by, about, on, at, in), use the object form whom in formal writing. Spoken English often drops this, so when editing decide whether to correct, rewrite, or accept the casual tone.

Quick answer

Use whom after prepositions or whenever the pronoun functions as the object. Use who when it's the subject of a clause.

Quick test: replace who/whom with he/him (or they/them). If him/them fits, use whom; if he/they fits, use who.
In formal writing, consider fronting the preposition: "To whom did you write?" In casual speech, ending a clause with who is common and usually accepted.
When in doubt, rewrite (e.g., "the person who," or move the preposition) to keep tone natural.

Core explanation: who vs. whom after prepositions

Who = subject (he/she/they). Whom = object (him/her/them). If the pronoun follows a preposition or is the object of a verb, use whom.

Test: Swap in he/him. "To who(m) did you speak?" → "I spoke to him" ⇒ whom.
Common prepositions to watch: to, with, for, from, by, about, on, at, in, of.

Common mistake patterns - wrong / right / neutral rewrites

Below are typical sentences showing the incorrect who, the corrected whom, and a neutral rewrite to avoid stilted phrasing.

Wrong: She gave the document to who?
Right: She gave the document to whom?Neutral: Who received the document?
Wrong: Who did you send the email to?
Right: To whom did you send the email?Neutral: Which person received the email?
Wrong: I don't know who he was talking to.
Right: I don't know to whom he was talking.Neutral: I don't know the person he was talking to.
Wrong: This is the person who I gave the notes.
Right: This is the person to whom I gave the notes.Neutral: This is the person I gave the notes to.
Wrong: He is someone who I can trust.
Right: He is someone whom I can trust.Neutral: He is someone I can trust.
Wrong: Who are you going with?
Right: With whom are you going?Neutral: Who are you going with? (casual)

Real usage and tone: when to correct vs. rewrite

Match your choice to the audience. Legal, academic, and some formal business writing prefer whom or a fronted preposition. In neutral business writing, a rewrite is often clearer. In casual speech and messaging, who at clause-ends is fine.

Formal: To whom should I address the invoice?
Neutral business: Who should I address the invoice to? (rewrite acceptable)
Casual: Who are you going with tonight? (text or spoken)

Work examples - formal + practical rewrites

Three workplace sentence pairs with a formal whom form and a friendlier rewrite.

Formal: With whom will the team coordinate the rollout?Practical: Who will coordinate the rollout with the team?
Formal: To whom should I address the invoice?Practical: Who should I send the invoice to?
Formal: Please tell me whom I should copy on the approval email.Practical: Please tell me who to copy on the approval email.

School and academic examples

Academic writing favors correct object forms or clear rephrasing that avoids awkwardness.

Whom did the professor invite to the symposium?
To whom should we send the recommendation letters?
The student to whom the award was given wrote an excellent paper.

Try your own sentence

Test the whole sentence with the he/him swap rather than the isolated phrase. Context clarifies whether the pronoun is subject or object.

Casual examples: texts, chats, and speech

Keep it simple in informal contexts; apply formal forms only when the tone calls for them.

Text: "Who are you texting?" - fine.
Text/spoken: "Who did you go with last night?" - common.
Spoken vs. written formal: "Who are you going with?" → formal written: "With whom are you going?"

Fix your sentence: step-by-step rewrites and templates

Use these moves to correct quickly: front the preposition; replace with "the person who"/"the people who"; convert to passive; or split the clause. Read aloud to check tone.

Template: Front the preposition - "Who did you send the files to?" → "To whom did you send the files?"
Template: Replace with "the person who" - "Who should I speak with?" → "Which person should I speak to about this?"
Template: Use a neutral noun - "I don't know who to invite." → "I'm not sure which people I should invite."
Examples:
Original: "I don't know who to invite." →
Formal: "I don't know whom to invite." → Safer: "I'm not sure which people I should invite."
Original: "Who did you send the files to?" →
Formal: "To whom did you send the files?" → Safer: "Who received the files?"
Original: "Who should I speak with about this budget?" →
Formal: "With whom should I speak about this budget?" → Safer: "Which person should I speak to about the budget?"

Memory tricks and editing habits

Fast checks to catch most errors while proofreading.

Him/He test: replace who/whom with him/he. If him fits, use whom.
Front the preposition mentally: "To whom..." clears up many cases.
Search your draft for who/whom and run the swap test on each occurrence.
When tone is at stake, prefer a rewrite over forcing whom into a casual sentence.

Hyphenation, spacing, and grammar notes

No hyphens or special spacing for who/whom. Use a single space after words and standard punctuation. Whom is declining in informal use; for formal documents, prefer correct object forms or clear rewrites.

No hyphens: don't write "who-m" or "whom-".
Punctuation: clauses with whom follow the usual comma rules.
Tip: don't confuse whose (possessive) with who's (who is).

Similar mistakes and other pronoun traps

Watch nearby pronoun issues that often appear with who/whom. The same he/him swap works for whoever/whomever.

Who vs. that/which: use who for people; that/which for things.
Whoever vs. whomever: test the role inside their clause - if the pronoun acts as subject, use whoever; if object, use whomever.
Possessive confusion: whose (possessive) vs. who's (who is).

FAQ

When should I use whom after a preposition?

Use whom when the pronoun is the object of the preposition or verb. If the pronoun is the actor (subject), use who. Apply the he/him swap to test.

Is "Who did you speak to?" acceptable?

Yes in casual speech and many informal writings. In formal writing prefer "To whom did you speak?" or a neutral rewrite that fits the tone.

How do I decide between whoever and whomever?

Apply the subject/object test inside their clause. Replace with he/him inside the clause: if he fits, use whoever; if him fits, use whomever.

Can I always rewrite to avoid whom?

Yes. Rewriting to remove the preposition or using "the person who" often produces clearer, more natural sentences.

Are grammar checkers reliable for this?

Grammar checkers catch many instances and suggest corrections or rewrites. Use them as a second pair of eyes and learn the he/him test to understand suggested changes.

Want quick fixes you can paste?

Copy a sentence into a checker to see recommended corrections and explanations, then apply a rewrite to match your tone. If you paste one sentence here, I can show the formal correction and two rewrite options (one neutral, one casual).