Both spellings refer to the same word with the same meaning. The question isn’t which one is correct in an absolute sense — it’s which one is appropriate for what you’re writing.
The short answer: Through is the standard spelling used in all formal, professional, and general writing. Thru is an informal shorthand, widely recognized but largely restricted to specific informal or commercial contexts.
What “Through” Means
Through is a preposition, adverb, and adjective with several related meanings:
- Movement from one side to the other: She walked through the door.
- Duration or completion: He slept through the night. I’m through with this project.
- By means of: We connected through a mutual friend.
- From start to finish: Read through the entire document.
It’s one of the most common words in English and has been spelled through in its current form since at least the 14th century. The spelling looks unusual relative to its pronunciation (/θruː/), which is why people look for a simpler version.
What “Thru” Is
Thru is a simplified spelling of through that matches how the word actually sounds. It isn’t a typo or a mistake — it’s a recognized informal variant that has appeared in American English since at least the early 20th century.
Dictionaries including Merriam-Webster list thru as an informal or simplified spelling, not as a separate word with a different meaning. It means exactly the same thing as through in every context where it appears.
You’ll see thru most often in:
- Drive-thru — the standard spelling on restaurant signage and in casual writing about fast-food lanes
- Text messages and informal digital communication
- Commercial signage where brevity matters
- Informal personal notes
The form drive-through also exists and is the more formal written version of the same thing.
Where Each Spelling Belongs
| Context | Use |
| Essays, reports, articles | through |
| Business writing, emails | through |
| Academic writing | through |
| News and journalism | through |
| Fiction and literature | through |
| Text messages, casual chat | either, but thru is common |
| Drive-thru signage | thru is standard |
| Social media (informal) | either |
The practical rule: if your writing would be reviewed by an editor, a teacher, an employer, or anyone evaluating its quality, use through. If you’re texting a friend or writing a sticky note, thru causes no confusion.
Is “Thru” Acceptable?
Yes, thru is a real and recognized spelling — but “acceptable” depends entirely on context.
Most style guides, including the Chicago Manual of Style and AP Style, treat thru as too informal for standard written English. That doesn’t make it wrong in the way that a misspelling is wrong. It makes it situationally inappropriate, the same way you might say gonna in conversation but write going to in a cover letter.
Some simplified spelling movements in the early 20th century actively promoted thru (along with forms like tho for though and lite for light). Lite stuck in product branding. Thru stuck in the drive-thru. Most of the others didn’t survive into mainstream use.
“Thru” in American vs British English
Thru is almost exclusively an American English informal variant. British English writing almost never uses it, even informally. If you’re writing for a British audience or in British English, stick to through in all contexts.
The One Case Where “Thru” Is Actually Standard
Drive-thru is the settled, standard spelling for the fast-food lane concept — more common in everyday writing than drive-through, even in relatively formal references to the thing. Both spellings are used, but if someone writes “I grabbed coffee at the drive-thru,” no one considers that an error.
Outside of that compound, thru reads as informal.
Quick Decision Rule
Ask yourself: Would I write “gonna” here?
If yes — casual enough for thru.
If no — use through.
Bottom line: Through is the correct spelling for standard writing. Thru is an informal variant that belongs in casual contexts and has earned a permanent home in drive-thru. Using thru in a formal document won’t confuse anyone, but it will signal informality — which is fine when that’s your intent, and worth avoiding when it isn’t.
Read more:
- Gluing or Glueing: Which Spelling Is Correct?
- Taught or Tought: Which Spelling Is Correct?
- Reinforce or Reenforce: Which Spelling Is Correct?
- Imbed vs Embed: Is There a Difference?
It’s Afini, I am the author at Vocab press, a website focused on animal facts with clear visuals and simple guides. I research and share accurate, easy-to-understand information for readers of all ages. My goal is to make learning about animals fun, trustworthy, and simple. I follow fact-based writing and keep content updated, helpful, and people-first. Thank you for reading.
