What does a grammar checker fix?
A grammar checker looks for mistakes that break the rules of standard writing: a verb that does not agree with its subject, a missing article, the wrong preposition, a comma splice, a sentence with no main verb. It also catches the surface errors that sit next to grammar, such as typos, capital letters and spacing.
What this checker does and does not do
The Grammar Checker sends your text to an AI model with one instruction: correct grammar, spelling and punctuation, change nothing else, and return the corrected text. Your original and the result are then compared in your browser so changed words can be highlighted.
That design has two consequences you should know about:
- It is a proofreader, not a style editor. Awkward but grammatical sentences usually stay as they are. Use the Sentence Rewriter for those.
- It can be wrong. No accuracy figure is claimed here, because none has been measured. Treat every highlight as a suggestion, especially for names, technical terms, quotations and deliberate choices such as dialect or fragments in fiction.
Common errors it looks for
| Error type | Before | After |
|---|---|---|
| Subject–verb agreement | The results of the survey is clear. | The results of the survey are clear. |
| Apostrophes | The company announced its' plans. | The company announced its plans. |
| Articles | She is an university student. | She is a university student. |
| Run-on sentence | I finished the draft I will send it tonight. | I finished the draft. I will send it tonight. |
| Capitalization | We meet on friday in london. | We meet on Friday in London. |
American or British English?
The checker keeps the spelling variety of your text, so colour stays British and color stays American. It does not force one variety, so if your school, employer or publisher requires one, run the Spell Checker afterwards with the matching variety. Merriam-Webster is the usual reference for American spelling and the Oxford dictionaries for British.
A quick proofreading routine
- Run the checker on one section at a time.
- Read the highlights and accept only the changes that keep your meaning.
- Read the final text aloud once: your ear catches what both tools and eyes miss.
- Check names, figures and quotations by hand.
Each run takes up to 6,000 characters, roughly 900 English words, so split long documents by section. If you are limited to one tool, remember that grammar tools do not check facts or judge whether an argument is good.