You've written a Korean sentence. Is it grammatically correct?
The honest answer for most learners: you can't tell yet — that's the whole problem. So you reach for a tool. The bad news: most "Korean grammar checkers" online are either machine translations dressed up as grammar tools, or basic spell-check that misses the things you actually need help with (particles, verb endings, formality level).
We tested every free Korean grammar checker we could find on the same sample sentences — ranging from beginner mistakes ("저는 학생 입니다") to intermediate errors (wrong particle, mismatched politeness level). Here's how they compare.
Quick Comparison Table
| Tool | Best For | Catches Particles? | Catches Politeness? | Free Tier |
|---|---|---|---|---|
| Pusan University 맞춤법/문법 검사기 | Native-level grammar check | ✅ | ✅ | ✅ (unlimited) |
| Naver 맞춤법 검사기 | Quick spelling + basic grammar | Partial | ❌ | ✅ (300 chars) |
| ChatGPT (GPT-4) | Explanation + correction | ✅ | ✅ | ✅ (limited daily) |
| Claude | Detailed explanation | ✅ | ✅ | ✅ (limited daily) |
| DeepL Write (Korean) | Style + flow | Partial | Partial | ✅ |
| Grammarly | ❌ Doesn't support Korean | ❌ | ❌ | n/a |
| LanguageTool | English + 20+ languages but Korean is basic | ❌ | ❌ | ✅ |
| HiNative | Native speaker correction (slow but accurate) | ✅ | ✅ | ✅ |
| HanCom 맞춤법 검사기 | Korean office workers' default | Partial | ❌ | Built into HanCom Office |
TL;DR ranking by use case:
- Best overall (free): Pusan University 검사기 — purpose-built for Korean
- Best for explanation: ChatGPT or Claude
- Best for native correction: HiNative (human-powered)
- Best for quick proofreading: Naver 맞춤법 검사기
- Don't bother: Grammarly (no Korean), LanguageTool (Korean coverage is minimal)
1. Pusan University Grammar Checker (부산대 맞춤법 검사기)
The gold standard. Built by Pusan National University's NLP lab and used by Korean publishers, journalists, and academics. It catches spacing errors, spelling, basic grammar, and offers usage explanations in Korean.
Pros:
- Catches subtle particle errors (을/를, 이/가, 은/는)
- Handles polite/formal level inconsistencies
- Explanations cite Korean grammar rules
- Unlimited input length
Cons:
- Interface is Korean-only
- No mobile app
- Explanations are in Korean — frustrating if you're a beginner
Who it's for: intermediate and advanced learners who can read Korean explanations.
2. Naver 맞춤법 검사기
Naver's built-in spelling + grammar tool. Fast, ubiquitous, and Korean speakers' default for casual writing.
Pros:
- Instant results
- Catches the most common spelling/spacing mistakes
- Free, no signup
- Works inside the Naver mobile app
Cons:
- 300-character limit per check
- Doesn't explain why something is wrong
- Misses subtle particle/politeness errors
3. ChatGPT (GPT-4 or GPT-4o)
Not a dedicated tool, but the best free option for explanations. Paste your Korean and ask: "Please check this for grammar and explain corrections in English."
Pros:
- Bilingual explanations (Korean + English)
- Catches particles, verb endings, politeness, register
- Handles long passages
- Can adjust tone ("make this more formal" / "more casual")
Cons:
- Free tier rate-limited
- Occasionally invents corrections that aren't actually wrong
Prompt template:
"Please check the following Korean sentences for grammar errors. For each correction, explain in English what the rule is and why my original was wrong. Korean: [paste here]"
4. Claude (Anthropic)
Similar to ChatGPT but often gives more detailed grammatical explanations. Particularly strong on politeness-level analysis.
Pros:
- Long context (you can paste an entire essay)
- Detailed reasoning chains
- Less prone to hallucinated corrections than smaller models
Cons:
- Free tier limits
5. DeepL Write (Korean)
DeepL's writing assistant supports Korean. Better at style/flow than strict grammar.
Pros:
- Suggests more natural phrasings
- Catches awkward word order
- Free with no signup
Cons:
- Misses some particle/conjugation errors
6. Grammarly
Verdict: Skip. Despite supporting many languages, Grammarly does not check Korean grammar as of 2026. If you see Grammarly suggested for Korean elsewhere, the recommendation is outdated.
7. LanguageTool
Multi-language grammar checker. Officially supports Korean but the rule coverage is sparse.
Pros:
- Open source, self-hostable
Cons:
- Korean rule set is small; misses most learner errors
8. HiNative
Not a grammar checker — a Q&A app where native speakers correct your writing for free. Slower (minutes to hours) but more accurate than any automated tool.
Pros:
- Real native correction
- Explanations in your native language
- Cultural notes ("grammatically correct but no one says it like that")
Cons:
- Not instant
- Quality depends on which native speaker answers
9. HanCom 맞춤법 검사기
If you write in HanCom (Korea's default office suite), the built-in checker is decent — comparable to Naver for spelling/spacing.
The Strongest Free Workflow
The combination we recommend:
- First pass: Pusan University checker for hard grammar errors
- Second pass: ChatGPT or Claude with the prompt template above for explanation and style polish
This catches more than any single tool and costs nothing. Total time: about 5 minutes per paragraph.
Beyond Tools: Other Ways to Check Your Korean
When tools fail you (and they will), three habits build accurate grammar over time:
- Keep a personal error log. Every time you make the same mistake twice, write the rule down. Patterns repeat.
- Read aloud. Many Korean grammar errors sound wrong even if they look fine on paper.
- Find a tutor for a 25-minute correction session. A native Korean teacher can fix in 25 minutes what would take you hours with tools alone. KTalk Live's free trial includes exactly this.
How We Tested
We submitted the same Korean sentences to each tool — ranging from beginner mistakes to nuanced intermediate errors. Each tool was scored on:
- Particle accuracy — did it catch wrong particles (을/를, 이/가)?
- Verb conjugation — did it catch wrong endings?
- Politeness consistency — did it flag mixed politeness levels?
- Explanation quality — did it explain why, or just correct silently?
The ranking above reflects these criteria.
What's Next
Once you have a checker workflow you trust, the bigger payoff is preventing mistakes in the first place. Solidify your verb endings with our Korean Verb Conjugation guide, or work on natural phrasing with How to Say No in Korean.