Free AI
grammar checker.
Paste any text and get a grammar score, corrected version and a full breakdown of every error — with the rule explained. Powered by GPT-4o. No signup, no word limit.
Your Text
HOW IT WORKS
Fix your grammar in 3 steps
Paste your text
Paste any text — an email, essay, blog post, cover letter or report. Up to 5,000 characters, no signup required.
Check grammar
Click Check Grammar. GPT-4o analyses your text for grammar, spelling, punctuation, clarity and style errors in seconds.
Review every fix
See your grammar score, the corrected text ready to copy, and a full breakdown of each error with the rule explained.
FEATURES
More than a spell check
GPT-4o grammar engine
Uses OpenAI's most capable model — not a rigid rule-based checker. It understands context, so it catches nuanced errors that basic tools miss.
Every correction explained
Each fix comes with the grammar rule behind it. You don't just get a corrected text — you learn why it was wrong. Grammarly charges for this.
Grammar score 0–100
An at-a-glance quality rating for your text. Track improvements as you revise. Excellent (90+), Good (75–89), Needs Work (60–74), Major Issues (<60).
5 error categories
Grammar, Spelling, Punctuation, Clarity and Style — each colour-coded and explained separately so you know exactly what kind of issues your writing has.
No word limit
Check up to 5,000 characters per request — roughly 700–800 words. No daily cap, no credit system, no plan required.
Free forever, no signup
No account, no browser extension, no monthly fee. Check as many documents as you need. ToolStack grammar checker is free forever.
Why grammar still matters — and why free tools fall short
Grammar errors cost more than you think. Studies consistently show that readers lose trust in content with frequent grammar mistakes — whether that's a client reading a proposal, a hiring manager scanning a cover letter, or a Google algorithm evaluating page quality. A single misplaced apostrophe in a subject line can drop email open rates. A run-on sentence in a landing page headline can double your bounce rate.
Most free grammar checkers address the surface problem without teaching you anything. They highlight errors — sometimes incorrectly — with no explanation of the underlying rule. You fix the flagged word, make the same mistake again next week, and never improve. ToolStack's grammar checker takes a different approach: every correction includes the grammar rule, so you understand what you got wrong and why.
Common errors the tool catches: subject-verb disagreement ("the team are" vs "the team is"), incorrect apostrophe use ("its" vs "it's"), comma splices, tense inconsistency, dangling modifiers, incorrect homophones ("affect" vs "effect", "there" vs "their"), missing articles, and overuse of passive voice. Unlike browser-based tools that only check spelling, this tool analyses full sentence structure and contextual meaning — the difference between a basic spell check and a professional copy-edit.
COMPARISON
ToolStack vs. Grammarly vs. Word
| FEATURE | ToolStack | Grammarly Free | Microsoft Word |
|---|---|---|---|
| Explanations per correction | ✓ Every fix | ✗ Paid only | ✗ None |
| AI model | GPT-4o | Proprietary | Rule-based |
| Grammar score | ✓ 0–100 | ✗ | ✗ |
| No signup required | ✓ Always | ✗ Account needed | ✗ Microsoft account |
| No browser extension | ✓ Web-based | ✗ Extension needed | ✗ Desktop app |
| 5 error categories | ✓ Included | Partial (free) | Spelling only |
| Free to use | ✓ Forever | Partial | Paid software |
FAQ
Frequently asked questions
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