Whom is retreating from everyday English, but it has not left formal writing yet. One substitution — he or him — tells you which word belongs, every time.
THE SHORT ANSWER
Use who when the word does the action, and whom when it receives it. The test: answer the question with he or him. If he fits, use who; if him fits, use whom — both end in m. ‘Who called?’ (he called). ‘To whom did you write?’ (I wrote to him).
English used to mark its pronouns by role: I/me, he/him, we/us, they/them. Most of those distinctions are still automatic for native speakers. Only one pair causes trouble — who/whom — because whom has been quietly leaving the spoken language for a century, and our ears no longer reliably supply it.
The he/him test
Strip the sentence down to a statement and substitute a pronoun you never get wrong. Questions work best: rearrange them into answers.
___ wrote this report? → He wrote this report. → Who wrote this report?
You sent the file to ___? → I sent it to him. → To whom did you send the file?
The memory hook writes itself: him and whom share their final m. If the answer needs an m, so does the question.
Where even careful writers slip
The classic trap is the inserted clause. In ‘the consultant who we hired’, people reach for whom because consultants feel like objects — but who is the subject of its own little clause here (‘we hired’ already has its subject). Run the test on the clause alone: we hired him, so strictly it is ‘the consultant whom we hired’. Contrast: ‘the consultant who called us’ — he called, so who is right.
When to let whom go
In emails, chat and most journalism, ‘who’ in object position now sounds natural, and hypercorrect ‘whom’ (‘Whom is calling?’) sounds worse than the informal choice. Reserve whom for three places: after prepositions in formal prose (‘to whom it may concern’), legal and academic writing, and anywhere your audience of editors expects it. Never begin a sentence with whom unless a preposition introduces it — ‘Whom did you call?’ is dying even in formal registers.
Style note — Meaanings follows the modern consensus: whom where grammar requires it in formal contexts, who everywhere it sounds natural. Consistency within a document matters more than either choice.
Frequently asked questions
Is ‘To Whom It May Concern’ still correct?
Yes — ‘to whom’ is the safest home for whom in modern English, because the preposition forces the object form. The phrase remains standard on open references and formal letters.
Is whom disappearing?
From speech, largely yes; from edited prose, slowly. Major style guides now permit who in most object positions, but none has deleted whom entirely.
