AI Grammar Checker
Commercial use OK
380+ models
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Model:
+ GPT-5, Claude, Gemini
Corrected text
Corrections explained
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Check grammar, spelling, and punctuation with AI for free.
How to Use AI Grammar Checker
1
Enter your input
Type text, upload a file, or describe what you want. No account needed.
2
Click generate
Our AI processes your request in seconds using the best open-source models.
3
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Download, copy, or share your result. Free for personal and commercial use.
Use this tool via API
Automate this tool from your own code. OpenAI-compatible REST endpoint, Bearer-token auth, no extra SDK required. Token costs match the web interface.
curl -X POST https://api.free.ai/v1/chat/ \
-H "Authorization: Bearer sk-free-..." \
-H "Content-Type: application/json" \
-d '{"model": "qwen7b", "messages": [{"role": "user", "content": "Summarize this: ..."}]}'Related Free AI Tools
AI Grammar Checker — FAQ
Free.ai Grammar Checker reads your text and returns (1) the fully corrected version and (2) a labeled list of every correction — original phrase, replacement, category (grammar / spelling / punctuation / style / tense / article / preposition), and a one-sentence explanation of the rule. Pick one of 4 modes (Strict proofread / Preserve voice / Academic / ESL-friendly), 5 English dialects (US / UK / Canadian / Australian / Any), and 10 source languages. Word-level diff view highlights exactly what changed.
Grammarly Premium is $12/mo ($144/yr). LanguageTool Premium is $5/mo but caps free use at 20,000 chars. Ginger Premium is $7.49/mo. ProWritingAid is $10/mo or $79/yr. Free.ai runs on our self-hosted GPUs with no monthly subscription — 5,000-word runs, unlimited dialects, and four purpose-built modes (including ESL and Voice-Preserving) instead of one generic checker. Grammarly's browser extension is genuinely better if you write in a browser all day; Free.ai wins on price, language coverage, and transparent rule explanations.
Preserve voice fixes ONLY clear, objective errors — articles (a/an/the), subject-verb agreement, tense, punctuation, capitalization, typos. It never touches sentence structure, word choices, or stylistic decisions. Use it when you want someone to proofread your writing without flattening it into generic "AI prose". Strict mode goes further and will suggest stylistic rewrites (weak verb → strong verb, passive → active, redundancy → cut); useful for first-pass editing, risky on finished drafts.
Three known failure modes: (1) Dialect-specific idioms occasionally get flagged in the "Any" dialect setting — pick your specific dialect. (2) Very long run-on sentences (60+ words) sometimes get split in ways that change emphasis — review diff mode carefully. (3) Creative punctuation (intentional comma splices for rhythm, em-dash heavy prose) gets normalized even in Preserve mode — spot-check the diff for intentional style.
Yes — the system prompt prioritizes the errors non-native speakers make most (articles, prepositions, agreement, count vs mass nouns, word order) and writes explanations in plain-English learner register rather than grammarian jargon. "You should use 'the' here because we're talking about a specific building" beats "definite article required with a restrictive post-modifier". Pair with /text/paraphraser/ Fluency mode for the full workflow.
Ten explicit picks: English, Spanish, French, German, Portuguese, Italian, Dutch, Chinese, Japanese, Arabic. Auto-detect works across all 99 Free.ai languages, but correction quality drops for lower-resource languages. For academic work in non-English, use /text/proofreader/ which adds style-layer editing on top of grammar.
Yes — punctuation (comma splices, missing Oxford commas, misplaced apostrophes, quote-style mixing), typos (the/teh, it's/its, your/you're, affect/effect), and hyphenation. The output labels each with its category so you can scan for a specific class quickly. Dialect setting matters: US vs UK quote conventions differ, and the checker respects your pick.
The system prompt instructs the model to preserve citations verbatim (APA, MLA, Chicago, footnote markers) and leave quoted material inside quotation marks alone. Always review the diff on academic work — no AI is perfect with nested brackets or unusual citation styles.
Up to 5,000 words (~40,000 characters) per run. For book-length proofreading, split by chapter — quality stays higher under 8K tokens of context. For PDF grammar checking, extract to text first and paste.
Text is sent to Free.ai's self-hosted GPUs, processed, and discarded. We do not train on user inputs. We log only timestamp + token cost for billing — never the source text. Generation history (signed-in users) stores a 200-char preview for your dashboard.
No — first check runs free, no email, no credit card. Sign up for 10,000 free signup tokens + generation history, higher daily caps, and access across all 400+ Free.ai tools.
Yes. POST to /v1/chat/ with the grammar-checker system prompt and parse the JSON response in your client. Useful for CMS plugins, code review of blog drafts, or automating a Slack proofreading bot. Full snippets at /api/.
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