A who/whom checker catches the mistake most people make

Who is the subject of a sentence — the person doing the action. Whom is the object — the person receiving the action or following a preposition. A who/whom checker flags when you use the wrong one, which matters because the error is visible to readers who notice grammar.

The confusion happens because English speakers rarely use "whom" in speech anymore. You might say "Who did you call?" even though the grammatically correct form is "Whom did you call?" A checker catches this gap between how we talk and how we write formally.

Most word processors have a grammar tool built in — Microsoft Word, Google Docs, and Grammarly all flag who/whom errors. Standalone checkers like Hemingway Editor and ProWritingAid also catch them. The difference is how clearly they explain why the error matters and what to change.

Key Takeaways

  • Who is the subject performing an action; whom is the object receiving the action or following a preposition like "to" or "for".
  • The easiest test is to replace the word with "he" (who) or "him" (whom) — if "he" works, use who; if "him" works, use whom.
  • Built-in checkers in Word and Google Docs catch most who/whom errors, but may not explain the rule clearly.
  • Grammarly and ProWritingAid provide explanations alongside the correction, which helps you learn the pattern.

The straightforward test that works every time

Replace the who/whom word with either "he" or "him" and read the sentence aloud. If "he" sounds right, use who. If "him" sounds right, use whom.

Example: "The manager spoke to [who/whom] arrived first." Replace with he/him: "The manager spoke to him arrived first" — that's wrong. Try the other way: "The manager spoke to he arrived first" — also wrong. The real issue is that the sentence needs restructuring, but the test still works: "Who arrived first?" uses who because "he arrived first" is correct.

Another example: "I don't know [who/whom] to contact." Replace: "I don't know him to contact" — that works. So use whom. The full sentence is "I don't know whom to contact."

This test works because English grammar for pronouns is consistent. He/she/they are subjects. Him/her/them are objects. Who and whom follow the same pattern, even though we stopped using whom in everyday speech.

What different checkers actually catch

Microsoft Word's grammar checker flags obvious who/whom errors in most cases. It will catch "Who did you call?" and suggest "Whom did you call?" However, it sometimes misses the error in complex sentences where the who/whom word is buried in a clause.

Google Docs has a similar built-in checker that works well for straightforward mistakes but may not catch every instance. Both tools show you the error but often don't explain the rule, which means you might accept the correction without understanding why.

Grammaly goes further by explaining the error in plain language. When it flags a who/whom mistake, it tells you whether the word is a subject or object and why the correction matters. This makes it useful if you want to learn the pattern rather than just fix individual sentences.

ProWritingAid also explains the reasoning and shows you a history of your who/whom errors across a document, which helps you spot whether you have a pattern of confusion. Hemingway Editor is simpler and focuses on clarity, so it may not catch every who/whom error but will flag the ones that affect readability.

When a checker might get it wrong

Checkers struggle with sentences where the who/whom word is far from the verb it relates to. Example: "The person [who/whom] I think should lead the project is Sarah." A basic checker might flag this as wrong because it sees "I think" and gets confused about what the who/whom word is doing. The correct answer is "who" because Sarah is the subject of the sentence, but the distance between the words can trip up automated tools.

Checkers also sometimes miss who/whom errors in questions that are phrased unusually. "Who is this letter for?" is technically "Whom is this letter for?" but many checkers let it pass because the error is so common in speech that the tool's training data includes it as acceptable.

The safest approach is to use a checker as a first pass, then explore the he/him test yourself to any flagged sentence. If you understand the rule, you can override the checker when it's wrong.

Why this matters for different types of writing

In formal writing — job applications, academic papers, professional emails — a who/whom error signals carelessness to readers who know the rule. It doesn't change the meaning of your sentence, but it does affect how seriously readers take your writing.

In casual writing — social media, text messages, blog comments — the error is so common that most readers won't notice or care. Many style guides now accept "who" in all positions because the language is shifting. However, if you're writing for an audience that values grammar precision, the distinction still matters.

For content writers and journalists, a checker is useful because it catches errors before publication. For students, understanding the rule matters more than relying on a tool, because you may not have access to a checker during an exam or timed assignment.

How to set up a checker and use it effectively

If you use Microsoft Word, the grammar checker is already on. Go to File > Options > Proofing and make sure "Check grammar" is turned on. Word will underline who/whom errors in blue as you type.

In Google Docs, the spell-check tool includes grammar. Click Tools > Spelling and grammar to run a full check, or enable "Show spelling suggestions" in the settings to see errors as you type.

If you want more detailed feedback, install Grammarly as a browser extension or desktop app. It works in most writing platforms and shows explanations for each error. ProWritingAid is a paid tool that integrates with Word and has a web editor; it's useful if you write frequently and want to track patterns in your mistakes.

The most effective approach is to run a checker after you finish writing, then review each flagged error using the he/him test. This way you learn the rule instead of just accepting corrections blindly.

Frequently Asked Questions

Is "whom" becoming obsolete?

In spoken English and casual writing, yes — most people use "who" in all positions now. However, formal writing still expects the distinction, and many readers notice the error. If you're writing for a professional or academic audience, using "whom" correctly shows attention to detail.

Can I just use "who" everywhere?

You can, and many people do. But in formal contexts, it reads as a mistake. If your audience includes people who know the rule, using "who" incorrectly will undermine your credibility. A checker helps you avoid this without having to memorize the rule.

Why do checkers sometimes disagree on who versus whom?

Different tools have different training data and rules. Some checkers are stricter about the formal rule, while others accept common speech patterns. If two checkers disagree, explore the he/him test yourself — that's the actual grammar rule, and it won't change between tools.

Does it matter if I use a checker or learn the rule myself?

Both approaches work. A checker is faster for catching errors in finished writing. Learning the rule takes more time upfront but means you won't need a tool for every sentence. Most writers benefit from doing both — use a checker to catch what you miss, and learn the pattern so you catch it yourself next time.