By Who or By Whom? Grammar Rules with Examples

Using by who or by whom correctly can feel confusing, even for fluent English speakers. The short answer is that “by whom” is grammatically correct because whom is the object pronoun used after a preposition like by.

However, in everyday spoken English, many people casually say “by who,” even though it is considered informal. This confusion happens because who and whom sound similar, and modern conversation often ignores traditional grammar rules.

In this guide, you’ll learn the difference, understand the history behind these pronouns, compare British English and American English usage, see real-life examples, avoid common grammar mistakes, and improve your writing skills for academic writing, business writing, and everyday communication.

Table of Contents

Quick Answer

By whom is the correct choice in standard English because the word by is a preposition, and a preposition should be followed by an object pronoun. Since whom is the object form of who, by whom is grammatically correct.

Correct examples:

By whom was this report written?
By whom were the invitations sent?
The project was completed by whom?

Informal examples:

By who was this written? ❌ (Informal and grammatically incorrect)
Who was this written by? ✅ (Natural in spoken English)

Quick Rule

Expression	Correct?	Best Used In
By whom	✅ Yes	Academic writing, professional communication, formal English
By who	❌ No (formal grammar)	Occasionally heard in casual spoken English

If you can replace the word with him or them, use whom.

By him → By whom ✅
By he → By who ❌

This simple test helps students, writers, editors, and English learners choose the correct pronoun with confidence.

The Origin of By Who or By Whom

The difference between who and whom comes from the history of the English language. Both words originated from Old English, where pronouns changed their forms depending on their role in a sentence. This system is known as the grammatical case.

Over time, everyday speech became simpler. Many speakers stopped using whom in casual conversation, while formal written English continued to follow traditional grammar usage.

Today:

Who usually works as the subject pronoun.
Whom works as the object pronoun.
After a preposition such as by, to, with, for, from, or about, whom remains the correct grammatical choice.

For example:

Who called you?
Whom did you call?
By whom was the decision made?

Although spoken English often replaces whom with who, major style guides still recommend whom in formal academic essays, research papers, professional emails, and business communication.

British English vs American English

Many learners wonder whether British English and American English treat by who and by whom differently.

The answer is simple: both varieties follow the same grammar rule.

In both countries:

By whom is the grammatically correct form.
By who appears mainly in informal conversation.
Modern speakers often avoid whom by rewriting the sentence.

For example:

Instead of:

By whom was the package delivered?

People often say:

Who was the package delivered by?

Although ending a sentence with a preposition was once discouraged, modern English grammar accepts it in most everyday situations.

British English vs American English Comparison

Feature	British English	American English
Formal writing	By whom is preferred	By whom is preferred
Casual conversation	Often replaced with Who…by?	Often replaced with Who…by?
Academic writing	Strong preference for by whom	Strong preference for by whom
Business writing	Uses by whom in formal documents	Uses by whom in formal documents
Spoken English	Whom is becoming less common	Whom is becoming less common

Whether you’re writing for readers in the United Kingdom, the United States, Canada, Australia, or other Commonwealth countries, by whom is still the safest choice in formal writing, while conversational English usually favors more natural sentence structures.

Pronunciation of By Who or By Whom

Although by who and by whom look different, their pronunciation is very similar. This is one reason many English learners and even native speakers confuse them.

Pronunciation

Phrase	Pronunciation	Sounds Like
By who	/baɪ huː/	“bye HOO”
By whom	/baɪ huːm/	“bye HOOM”

The only noticeable difference is the “m” sound at the end of whom.

Why pronunciation causes confusion

In fast spoken English, the final m in whom can be soft or almost disappear. As a result, listeners may hear by who instead of by whom.

For example:

By whom was the award presented? ✅
By who was the award presented? ❌

When speaking casually, many people avoid this confusion by changing the sentence:

Who presented the award? ✅
Who was the award presented by? ✅

This is one reason who is much more common in everyday conversation, while whom remains important in formal English.

Why People Confuse By Who or By Whom

The confusion between by who and by whom has existed for years. Even experienced writers sometimes pause before choosing the correct word.

Here are the biggest reasons people mix them up.

1. Who is used more often

In everyday conversation, who appears much more frequently than whom. Because people hear who every day, they naturally use it in places where whom is actually correct.

Example:

By who was this painting created? ❌
By whom was this painting created? ✅

2. Many speakers rarely use “whom”

Modern spoken English has become less formal. Most conversations replace whom with who, especially on social media, in text messages, and during casual conversations.

Example:

Who are you talking to? ✅ (Common)
To whom are you talking? ✅ (More formal)

Both are understood, but the second follows traditional grammar rules.

3. People forget subject and object pronouns

The most common grammar mistake is not knowing whether the pronoun is acting as the subject or the object.

Remember:

Who = Subject pronoun
Whom = Object pronoun

Examples:

Who called the manager? ✅ (Subject)
Whom did the manager call? ✅ (Object)
By whom was the contract signed? ✅ (Object after a preposition)

Understanding sentence structure makes this rule much easier.

4. Prepositions require object pronouns

Words such as by, to, with, for, from, about, after, before, and between are prepositions.

After a preposition, English normally uses an object pronoun.

Examples:

by whom ✅
with whom ✅
to whom ✅
from whom ✅

This is why by who is not considered correct in standard English.

5. Informal English influences writing

Many people write exactly as they speak.

While casual speech often ignores traditional grammar, academic writing, professional communication, business writing, and research papers still expect correct grammar usage.

Choosing by whom in formal situations makes your writing sound more polished and professional.

Which Spelling Should You Use?

The correct choice depends on your audience and the type of writing.

If you’re writing an important document, following standard English is always the safest option.

Use By Whom for:

Academic writing
Business writing
Professional emails
Research papers
Legal documents
Formal reports
Official letters
Published articles

Examples:

By whom was the policy approved?
By whom were the results verified?
By whom was the payment authorized?

These sentences follow formal English grammar and are appropriate for professional documents.

Avoid By Who in formal writing

Although many native speakers say by who, grammar experts still consider it incorrect after the preposition by.

Instead of writing:

❌ By who was this article written?

Write:

✅ By whom was this article written?

Or rewrite naturally:

✅ Who wrote this article?

This version is grammatically correct and sounds more natural.

Advice for different audiences

Audience	Best Choice
Students	By whom
English learners (ESL/EFL)	By whom
Teachers	By whom
Writers and editors	By whom
Professional communication	By whom
Casual conversation	Usually rewrite the sentence instead of using either phrase

Following this simple advice will improve your writing skills, strengthen your English communication, and help you avoid common grammar mistakes in both formal and informal situations.

Common Mistakes with By Who or By Whom

Many people know that who and whom are different, but they still use the wrong one because they focus on how the sentence sounds instead of its grammar structure. The easiest way to avoid mistakes is to identify whether the pronoun is the subject or the object.

Incorrect	Correct	Why?
By who was the book written?	By whom was the book written?	By is a preposition, so it takes the object pronoun whom.
By who were you invited?	By whom were you invited?	Whom is the object of the preposition by.
By who was the decision made?	By whom was the decision made?	Formal English requires whom after a preposition.
Who did you send the letter to?	To whom did you send the letter? (formal) / Who did you send the letter to? (natural)	Both are acceptable, depending on the level of formality.
Whom called you yesterday?	Who called you yesterday?	Who is the subject of the verb called.

Common grammar tips

Use who when the pronoun performs the action.
Use whom when the pronoun receives the action.
After a preposition such as by, to, with, from, or for, use whom in formal writing.
If the sentence sounds too formal, rewrite it instead of forcing whom into casual speech.

By Who or By Whom in Everyday Examples

Understanding the rule becomes much easier when you see how it works in real situations.

In emails

Formal:

By whom should this invoice be approved?

Natural:

Who should approve this invoice?

In business writing

By whom was the agreement signed?
By whom were the meeting notes prepared?
Who prepared the meeting notes? (more natural)

In news reports

The investigation is being led by whom? ❌
By whom is the investigation being led? ✅
Who is leading the investigation? ✅ (preferred by many news organizations)

On social media

People rarely write by whom because conversations are informal.

Examples:

Who made this?
Who designed this?
Who posted this?

While you may occasionally see by who, it is considered non-standard in formal English.

In academic writing

Academic writing follows traditional grammar rules, so by whom is still preferred.

Examples:

By whom was the theory first proposed?
By whom was the experiment conducted?
By whom were the data collected?

Using by whom correctly makes research papers, academic essays, and professional documents sound more accurate and polished.

Easy Trick to Remember By Who or By Whom

You don’t need to memorize complicated grammar rules. Use this simple memory trick.

The “He/Him” Test

Replace the pronoun with he or him.

If he fits, use who.

If him fits, use whom.

Examples:

Who wrote the article?

He wrote the article. ✅
Him wrote the article. ❌

Answer: Who

By whom was the article written?

The article was written by him. ✅
The article was written by he. ❌

Answer: Whom

Another easy rule

Think of this sentence:

By + Whom

Whenever you see a preposition like:

by
to
with
for
from
about
after

your first choice in formal English should be whom.

Quick memory chart

If you can replace it with…	Use…
He / They	Who
Him / Them	Whom

This simple trick is used by teachers, editors, proofreaders, and professional writers because it works almost every time.

By Who or By Whom – Google Trends & Usage Data

Search interest shows that “who” is overwhelmingly more common than “whom” because modern English favors simpler sentence structures. Many users search “by who or by whom” because they want to know which form is grammatically correct before writing an email, essay, report, or professional document.

In countries such as the United States, United Kingdom, Canada, Australia, and India, searches for who vs whom increase during school terms and exam periods, as students and English learners (ESL/EFL) review grammar topics.

In everyday communication:

Who dominates casual conversation and social media.
Whom remains common in academic writing, legal documents, formal reports, and professional communication.
Many modern writers avoid the issue altogether by rewriting the sentence naturally.

Comparison Table

Feature	By Who	By Whom
Grammatically correct after by	❌ No	✅ Yes
Formal English	❌ Not recommended	✅ Recommended
Informal conversation	Sometimes heard	Less common
Academic writing	❌ Avoid	✅ Preferred
Business writing	❌ Avoid	✅ Preferred
Professional emails	❌ Avoid	✅ Preferred
Spoken English	Common but informal	Formal and less frequent
Object after a preposition	❌ Incorrect	✅ Correct

FAQs

Is by who ever correct?

In standard English, no. After the preposition by, the correct object pronoun is whom. While you may hear by who in casual conversation, it is considered grammatically incorrect in formal writing.

Why do people still say by who?

Many native speakers use who in everyday spoken English because it sounds more natural. Modern conversation often favors simpler grammar, but formal written English still follows the traditional rule of using whom after a preposition.

Is by whom old-fashioned?

Not at all. Although it is less common in casual speech, by whom is still widely used in academic writing, business writing, legal documents, professional reports, and other formal contexts. It remains part of standard English.

How can I quickly decide whether to use who or whom?

Use the he/him test:

If he fits, use who.
If him fits, use whom.

Example:

Who called you? → He called you.
By whom was the letter signed? → The letter was signed by him.

Can I rewrite the sentence instead of using whom?

Yes. In many cases, rewriting the sentence makes it sound more natural.

Instead of:

By whom was the meeting organized?

You can write:

Who organized the meeting?

Both are correct, but the second version is more common in everyday English.

Do British English and American English use different rules?

No. Both British English and American English follow the same grammar rule: by whom is correct after the preposition by. The main difference is that everyday speakers in both varieties often choose more natural sentence structures instead of using whom.

Should English learners use whom?

Yes. If you’re studying English grammar or writing academic essays, research papers, professional emails, or formal documents, learning when to use whom will improve your writing skills and help you communicate more accurately.

Conclusion

The choice between by who or by whom is actually straightforward once you understand the role of subject and object pronouns. Because by is a preposition, it should be followed by the object pronoun whom, making by whom the grammatically correct form in formal English.

Although many people use by who in casual conversation, it is best avoided in academic writing, business communication, and professional documents. If you’re unsure, use the he/him test or simply rewrite the sentence in a more natural way. By following these simple grammar rules, you’ll write clearer, more confident English and avoid one of the most common pronoun mistakes.