Runs in your browser. Your files and text never leave your device - nothing is uploaded.
Free Online Grammar Checker
The Tools Kit’s free Grammar Checker proofreads your text for the small mechanical mistakes that slip through when you write quickly: doubled words, stray spaces, punctuation in the wrong place, a missing capital at the start, and commonly confused words like their/there or its/it’s. Paste an email, essay, or blog post, click Check Grammar, and every flagged item appears with a snippet of the text around it.
It is a rule-based grammar check, not an AI rewriter. The checks run in your browser, so your text is never uploaded, and there is no signup or word limit. Because the rules are fixed patterns, the results are predictable: the same text always gets the same report.
How to Check Your Grammar Online
- 1
Paste your text
Paste or type the text you want to proofread into the Your Text box. There is no word limit.
- 2
Click Check Grammar
The checker scans the text in your browser and shows a summary of how many issues and style notes it found.
- 3
Review each flagged item
Every item shows a short message and a snippet of the surrounding text. Red items are mechanical errors; amber items are style notes to double-check.
- 4
Fix and check again
Correct the text in the box. Editing hides the old results, so click Check Grammar again until the list comes back clean.
What the Grammar Checker Looks For
Every check falls into one of two groups. Errors are mechanical problems that are almost always wrong; style notes are words and phrasing worth a second look.
| Check | Type | What gets flagged |
|---|---|---|
| Extra spaces | Error | Two or more spaces in a row, including two spaces after a period |
| Repeated word | Error | The same word twice in a row, such as "the the" or "is is" |
| Space before punctuation | Error | A space before a period, comma, exclamation mark, question mark, semicolon or colon |
| Repeated punctuation | Error | Runs such as "!!", ",," or "...." (a three-dot ellipsis, "?!" and "!?" are allowed) |
| Missing space after punctuation | Error | A period, comma, exclamation or question mark followed directly by a capital letter, as in "closed.It" |
| Lowercase sentence start | Error | Text whose opening sentence begins with a lowercase letter |
| Possible passive voice | Style note | A form of "to be" followed by a word ending in -ed, such as "was finished" |
| Commonly confused word | Style note | Any use of their/there/they’re, your/you’re, its/it’s, then/than, affect/effect, loose/lose, to/too/two, weather/whether, accept/except, principal/principle or complement/compliment |
As a worked example, “We went to the the store .It was closed!!” produces four errors (the repeated “the”, the space before the period, the missing space before “It”, and the doubled exclamation mark) plus two style notes: “to” as a commonly confused word and “was closed” as possible passive voice.
Commonly Confused Words: Their, There, and They’re
Homophones are the mistakes spell check never catches, because every word is spelled correctly. That is why the checker flags each use of eleven easily mixed-up groups and asks you to confirm the choice. A few quick tests settle most of them:
- their / there / they’re: “their” shows ownership, “there” is a place, and “they’re” always means “they are”.
- its / it’s: if “it is” or “it has” fits, use “it’s”; otherwise use the possessive “its”.
- your / you’re: “you’re” means “you are”; “your” means something belongs to you.
- then / than: “then” is about time or sequence, “than” is for comparisons.
- affect / effect: usually “affect” is the verb and “effect” is the noun, the result.
- loose / lose: “loose” is the opposite of tight; “lose” is the opposite of win or find.
The remaining groups are to/too/two, weather/whether, accept/except, principal/principle, and complement/compliment. Because the checker cannot read meaning, a correctly used word still gets a note, so treat the list as a prompt to reread rather than a list of mistakes.
Passive Voice and Other Style Notes
Passive voice puts the action before the person doing it: “The report was finished by Sam” instead of “Sam finished the report.” It is not a grammar error, but active sentences are usually shorter and clearer, which is why the checker marks possible passive voice as a style note. The rule looks for is, are, was, were, be, been, or being followed by a word ending in -ed, so it catches “was approved” but not irregular forms like “was written”, and it can flag an adjective such as “is tired”.
For a broader look at clarity, run the same text through the readability checker to see sentence length and reading-ease scores, or use the essay checker, which applies these grammar rules alongside a word count and a Flesch reading-ease score in one report.
What a Rule-Based Grammar Check Cannot Catch
Pattern rules are good at mechanical slips but blind to meaning. This tool does not check spelling, subject-verb agreement, verb tense, comma placement inside a sentence, or word order, and it does not rewrite anything for you. It also reads only the very start of the text for a missing capital, and the confusable-word check matches straight apostrophes (it's) but not curly ones (it’s).
A good proofreading routine combines this check with your word processor’s spell check and a slow read-through out loud. If a sentence still sounds awkward, the paraphrasing tool can suggest alternative wording, and the text compare tool shows exactly what changed between your draft and the revised version.
Common uses
- Proofreading an email, cover letter, or social post before sending it
- Catching double spaces and doubled words in an essay or assignment draft
- Reviewing their/there, its/it’s, and then/than in a first draft
- Cleaning up text pasted from a PDF or another document, where spacing often breaks
- A final mechanical pass on blog posts and product descriptions
For school and publishing work, pair it with the word counter to stay within a word limit, the case converter to fix headings typed in the wrong case, and the citation generator for your reference list. More are collected under writing and citation tools.
Frequently Asked Questions
Yes. The Grammar Checker is free to use with no signup, no word limit and no daily cap on how many times you check your text.
No. The checks run as JavaScript in your browser, so the text you paste is never sent to a server or saved. Clearing the box or closing the tab discards it.
No. It uses fixed pattern rules rather than an AI or language model. That makes it fast and predictable for mechanical slips such as doubled words and spacing, but it does not understand meaning, so it cannot judge things like subject-verb agreement or tense.
No. There is no dictionary-based spell check. The tool focuses on spacing, punctuation, repeated words, sentence capitalization, possible passive voice and commonly confused words. Use your browser or word processor spell check alongside it.
Errors, shown with a red border, are mechanical problems such as extra spaces or a repeated word that are almost always wrong. Style notes, shown in amber, are things worth a second look, such as possible passive voice or a commonly confused word, that may be perfectly correct in context.
Commonly confused words such as their, its, then and to are flagged every time they appear, because the checker cannot read the sentence for meaning. If you used the right word, ignore the note. That is why these are style notes and not errors.
Use it's only when you can expand it to "it is" or "it has", as in "it's raining". Use its for possession, as in "the dog wagged its tail". The checker flags both forms so you can run that quick substitution test.
It flags likely passive voice when a form of "to be" (is, are, was, were, be, been, being) is followed by a word ending in -ed, such as "was approved". Irregular forms like "was written" are not caught, and phrases like "is tired" can be flagged even though they are not passive.
One space is the standard in modern style guides, including APA, MLA and Chicago. The checker reports two or more spaces in a row as an error, so it will catch double spacing after periods.
No. It lists each issue with a message and a snippet of the surrounding text, and you make the fix yourself in the text box. Editing hides the old results, so click Check Grammar again to confirm the fix.
No. There is no word or character limit. Very long documents take a little longer to check because everything is processed on your own device.
Reviewed by Raja Jahangir · Last reviewed: October 2, 2026
How do you check text for grammar mistakes online?
To check grammar, paste the text and click Check Grammar. Rule-based checks flag repeated words, double spaces, spaces before punctuation, missing spaces after punctuation, repeated punctuation, and a lowercase letter at the start of the text as errors, and mark possible passive voice and commonly confused words like their, there, and they're as style notes. Checking runs in the browser.
Does the grammar checker use AI?
No. The checks are pattern rules, not a language model, so they catch mechanical slips such as "the the", stray spaces, and "its" versus "it's" reliably, but they do not judge meaning or subject-verb agreement. For important writing, pair a rule-based check with a careful human read or a full editor.