Grammar Checker

You paste a text or upload a document, and a moment later it comes back with every mistake underlined in the text itself. Each one has a card on the right: the passage as written, the correction proposed, the family of the mistake — spelling, grammar, verb form, word choice, punctuation, syntax, style — and the rule involved, explained in one sentence. You apply the corrections you agree with, ignore the others, and copy the corrected text.

The checker spots mistakes; it does not rewrite. That distinction is the whole design. A tool that returns a 'corrected' version of your text has, in practice, rewritten it — changed words that were fine, smoothed phrases that were yours — and you have no way of telling what was a correction and what was a preference. Here every change is a separate, visible decision, and the text is yours until you accept one.

The underlining is exact. The tool finds each faulty passage in your text character by character before showing it, and a passage it cannot locate with certainty is dropped rather than placed approximately. A missing correction is invisible; a correction underlined at the wrong spot would destroy your trust in every other one.

• paste a text or upload a PDF, Word or text document
• every mistake underlined in place, with the rule explained
• accept or ignore each correction; nothing changes until you do
• ten thousand characters per check, no sign-up

Spelling covers misspelled words, dropped letters and, in languages that use them, missing accents. Grammar covers agreement — subject and verb, noun and adjective, singular and plural — and wrong articles or prepositions. Verb form covers tense, mood, endings and irregular forms: 'he go', 'I have went', 'if I was'. These three families are underlined in red, because they are mistakes in the plain sense: a reader will notice them and think less of the text.

Word choice catches the confusable pairs that spell checkers miss because both words exist: their and there, its and it's, affect and effect, than and then, lose and loose. Punctuation covers commas, periods, capitals after a period and apostrophes in contractions — underlined in amber, since some of these are matters of convention.

Syntax flags a missing word, an extra word or a construction that does not hold together. Style — repetition, heaviness, redundancy, an unidiomatic phrase — is always marked as a suggestion, never as an error, and shown in blue. You can ignore every style suggestion and still have a correct text; that is the point of separating them.

• red: spelling, grammar, verb form, word choice — real mistakes
• amber: punctuation — partly convention
• blue: syntax and style — suggestions you may decline

Most checkers tell you what to change. This one also tells you why, in one sentence written for someone who wants to understand rather than just fix: 'The past participle used with the auxiliary have agrees with a direct object placed before the verb', or 'Its is possessive; it's is the contraction of it is'.

There are two reasons for this. The first is that a correction you understand is one you will not need next time — the checker is, quietly, a teacher. The second is that a rule lets you disagree. If the explanation does not apply to your sentence — a proper noun, a deliberate colloquialism, a term of art — you can ignore the correction with confidence rather than accept it because the tool said so.

The rule is written in the language of this page, whatever the language of the text you check.

You do not have to copy and paste. Upload a PDF, a Word (.docx) or a plain text file of up to eight megabytes, and the text is extracted and checked exactly as if you had pasted it. When you are done, copy the corrected text back into your document.

Scanned PDFs are the one exception: a photographed page saved as PDF holds an image, not text, and nothing can be extracted from it. Open the original, select the text if you can, and paste it. Very long documents are checked up to ten thousand characters — three to four pages — and the result tells you if the text was cut. Check a longer document section by section; you will also find the list of corrections easier to work through.

Each card has two buttons: Apply and Ignore. Apply replaces the underlined passage with the correction, in green, in the text; Ignore fades the card and leaves the text as it was. Both can be undone. 'Fix everything' applies every correction you have not ignored, which is the fast path for a text with many small mistakes.

Nothing you do here changes your reference text. Corrections are applied to the display, and the corrected text is only assembled when you copy it. This is why you can change your mind about any correction at any point without the others moving: the positions were computed once, on the original, and stay valid.

The score at the top — out of a hundred — reflects the density of real errors, not suggestions. It is a rough guide, useful to see a text improve as you work, not a grade.

The checker corrects a text in its own language. Paste English and you get English corrections; paste Spanish, Portuguese, German, French or another language and the mistakes of that language are found — agreement, conjugation, accents, gender — with the rule explained in the language of this page.

Quality is highest in English and the major European languages. For French text specifically, the checker adds a set of deterministic typography rules that no language model handles well: the non-breaking space before a colon or question mark, the spaces inside « French quotation marks », the curly apostrophe. These are shown as suggestions in their own family, and can be ignored wholesale for a text destined for an English-speaking medium.

Proper nouns, brands, product names and technical terms are not touched, even when they look like misspellings — a checker that 'corrected' a surname or a chemical name would be worse than none. Deliberate foreign words are left as they are. And a correct sentence is left alone: the instruction to the checker says in so many words that finding no mistake is a valid answer.

The checker also does not rephrase. Replacing a correct word with a synonym is not a correction, and a proposed change that turns out to be a rewrite of a long passage rather than a fix is discarded before you see it. If you want your text rewritten — shorter, more formal, more natural — that is the job of the paraphrasing tool, which does exactly that and nothing else.

Run the finished essay through the checker last, after the content is settled. Work through the red cards first: those are the mistakes a marker will count. Then the amber ones. Read each rule as you go — the pattern of your own mistakes will show quickly, and the next essay will have fewer of them.

Treat the blue style suggestions with judgement. Some will improve a sentence; some will flatten a phrase you chose on purpose. An essay in your own voice with a few unusual constructions is better than one sanded smooth. The checker separates the two families precisely so you can make that call.

One more thing: a checker corrects language, not argument. A paragraph that is grammatically perfect and says nothing will pass unchanged. Use it for what it does, and read your own work for the rest.

A mistake in an email to a client, a cover letter or a report is noticed out of all proportion to its size. The checker is fastest on exactly these texts: a few paragraphs, checked in seconds, with each correction one click away. Paste, apply what you agree with, copy back.

For a cover letter or an application, run the checker and then read the text once more yourself, aloud if you can. The checker will catch 'their' for 'there' and a missing comma; it will not catch a sentence that is correct and clumsy, or a claim you cannot back up. And it will not flag a proper noun you spelled wrong, because it cannot know how the company spells its name — check those by hand.

Writers use the checker as a first pass before a human edit, to clear the mechanical mistakes and leave the editor's attention for what matters. Editors use it on submitted copy the same way. In both cases the point of separate, explained corrections is that the tool never silently changes a phrase the writer chose.

For people writing in a language that is not their own, the rules on each card are the most useful part. A non-native writer tends to make the same handful of mistakes — articles, prepositions, a tense — over and over, and seeing the rule each time is how those fade. The checker works on the text in its own language, so it can be used the other way too: a native English speaker writing in Spanish gets Spanish corrections with English explanations.

Ten checks a day without an account, each on up to ten thousand characters — three to four pages. That covers a student's essay, a professional's day of emails and a short report. No card, no email, no sign-up.

A free account multiplies both limits by four. The counter runs over a rolling twenty-four hours and is applied by account and by network. There is no paid tier for the checker: the limits keep the service fast for everyone, they do not sell a bigger version.

The text is sent to the server, analysed, and the corrections are returned. It is not stored, not added to any dataset, and not used to train anything. Uploaded documents are read in memory and discarded; the file is never written to disk. The only record kept is a usage counter for the daily limits.

The analysis is done by a language model hosted under a business agreement that excludes training on submitted text. If you check confidential material — a contract, a medical letter, an unpublished manuscript — this is the policy that applies.

This is a technical point, but it explains something you will notice: the underlines here are never a few characters off. Language models cannot count characters reliably — measured on a public benchmark, they get character positions right only a third to two-thirds of the time. A checker that asks a model 'where is the mistake' and underlines the answer will be wrong about a third of the time.

This checker never asks for a position. It asks the model to copy the faulty passage exactly, with a few characters of context on each side, and then finds that passage in your text itself. If the passage cannot be found — because the model altered an apostrophe or a space while copying — the correction is dropped rather than guessed. The result is that what you see underlined is what the correction is about, every time.

The grammar checker corrects mistakes and changes nothing else. The paraphrasing tool rewrites a text in different words, optionally in a different register or at a different length. The summarizer shortens a long text by keeping its important sentences. The AI detector and plagiarism checker change nothing and only report — whether a text looks generated, and whether it exists elsewhere online.

So: a text that says what you want but has mistakes — grammar checker. A text that is correct but must be said differently — paraphraser. A long text to shorten — summarizer. A text whose origin you doubt — detector or plagiarism checker.

The checker works on prose. Tables, code and formulas are not its job and may attract corrections that make no sense there; take them out before pasting. Very short texts — under twenty characters — are refused, because there is nothing to check. Texts over ten thousand characters are cut, and the result says so.

A checker does not guarantee the absence of mistakes. It catches the great majority of language errors and a good share of style problems; it can miss a subtle one, and it cannot check facts, names, figures or logic. Read your text once yourself after the corrections. Between the two — the tool and your reading — very little gets through.

• prose only: remove tables, code and formulas first
• twenty characters minimum, ten thousand maximum per check
• names, figures and facts are not checked — read those yourself

A few families account for most of what the checker finds in English text. Confusable words lead: their/there/they're, its/it's, your/you're, then/than, affect/effect, lose/loose, to/too. They pass every spell checker because both words exist; this checker reads the sentence and knows which one it needs. Subject–verb agreement comes next, especially with a phrase between the subject and the verb — 'the list of items are' — and with collective nouns.

Apostrophes in plurals ('apple's for sale'), missing commas after an introductory clause, a comma splice joining two sentences, and capitals after a period are the common punctuation findings. Verb forms — 'have went', 'if I was', 'should of' — and prepositions ('different than', 'depend of') round out the list. Every one of these comes with its rule, and after a few checks most writers stop making the ones they make most.

In other languages the profile changes: gender and number agreement dominate in Spanish, Portuguese and French; case endings and separable verbs in German; affixes in Indonesian. The checker corrects each language by its own rules.

• confusable words: their/there, its/it's, affect/effect
• subject–verb agreement, especially across a phrase
• apostrophes, comma splices, capitals after a period
• verb forms and prepositions

Punctuation is where the line between error and preference is finest, and the checker draws it deliberately. A missing period, a lowercase letter after one, an apostrophe in a plural, a comma splice: those are marked as errors, because every reader will read them as errors. A comma before 'and' in a list — the serial comma — is a convention that differs between publishers, and the checker does not impose one. A dash where a colon would do, a semicolon where a period would do: suggestions at most.

This is why punctuation is underlined in amber rather than red. Look at each one, read the rule, and decide. A house style — your institution's, your employer's, your publisher's — overrides the checker, and the checker is built so that it can.

'Colour' and 'color', 'organise' and 'organize', 'centre' and 'center' are both correct, in their respective conventions. The checker does not mark a text for using one or the other. What it does flag is a text that mixes them — 'colour' in one paragraph and 'color' in the next — because inconsistency is a mistake in either convention, and it is the kind of thing that creeps in when a text is assembled from several sources.

If you need a text converted from one convention to the other, that is a rewrite job rather than a correction: paste it into the paraphrasing tool with a note in your own head that Standard mode preserves spelling conventions, or do it by hand with search and replace. The checker will then confirm the result is consistent.

A text translated by a person or a tool often carries the fingerprints of the source language: a preposition that is right in French and wrong in English, a word order that sounds foreign, a false friend ('actually' for 'currently', 'eventually' for 'possibly'). The checker reads the text in its own language and flags those — as grammar, word choice or syntax, with the rule — which makes it a good last pass on anything that was translated before it goes out.

A sequence that works well: translate with the AI translator on this site in the register you need, then run the result through the checker in the target language, then read it once. The translator will have got the meaning; the checker will have caught anything that still sounds like the source; your reading catches the tone.

Paste this: 'Their are three reason why the project failed. First, the team were not given enough time, second the budget was cut in half, and third, nobody had clear responsibilitys. Its a shame because the idea itself were good and could of worked with better planning.' The checker returns eight cards.

'Their' → 'There' (word choice: their is possessive, there indicates place or existence). 'reason' → 'reasons' (grammar: plural after 'three'). 'team were' → 'team was' (grammar: a collective noun takes a singular verb in American English; marked as a suggestion, since British usage allows the plural). 'second the budget' → 'second, the budget' (punctuation). 'responsibilitys' → 'responsibilities' (spelling). 'Its' → 'It's' (word choice: contraction of it is). 'idea itself were' → 'idea itself was' (grammar: singular subject). 'could of' → 'could have' (verb form: 'of' is a mishearing of 'have').

Apply all eight and the paragraph reads: 'There are three reasons why the project failed. First, the team was not given enough time, second, the budget was cut in half, and third, nobody had clear responsibilities. It's a shame because the idea itself was good and could have worked with better planning.' Nothing else was touched — the argument, the tone and the slightly informal 'it's a shame' are exactly as written. That is what a checker, as opposed to a rewriter, does.

Most writing mistakes that reach a reader are not mistakes of knowledge but of haste: the writer knew the rule and did not look. A short routine catches nearly all of them. Write the text. Leave it for a minute if you can. Paste it into the checker and work through the red cards, then the amber ones. Copy the corrected text back. Read it once, aloud or under your breath, from the first word to the last. Send.

The reading is not optional, and it is the step people skip. The checker catches language; reading catches everything else — a sentence that is correct and unclear, a paragraph in the wrong order, a claim you cannot support, a tone sharper than you meant. Five minutes for an email, fifteen for a letter, an hour for a report. Nothing else you can do for a text costs so little and returns so much.

• write, then leave it for a minute
• check: red cards first, then amber, then blue if you want
• copy back and read once, start to finish

The score at the top of the result reflects the density of real errors — not suggestions — per hundred words, and a text with no errors scores 100. It is tempting to treat that as the target and to accept every card until the number stops moving. Resist it. The score is there to show a text improving as you work, and to give a rough sense of whether a piece needs a light pass or a heavy one.

A text with a score of 96 and its own voice is better than one with a score of 100 that has been sanded smooth by accepting every style suggestion. The checker separates errors from suggestions and colours them differently for exactly this reason. Fix what is wrong; consider what is suggested; keep what is yours.

Grammar checker, spell checker, proofreader: overlapping names for a tool that finds mistakes in a text; this one does all three. Agreement: the matching of subject and verb, or noun and adjective, in number, gender or person. Confusable words or homophones: words that sound alike and are spelled differently — their and there. Comma splice: two complete sentences joined by a comma alone. Register: the level of formality of a text; the checker does not change it, the paraphrasing tool does.

Suggestion: a proposed change that is a matter of style or convention rather than correctness, shown in blue or amber and safe to decline. Error: a change every reader would agree is a correction, shown in red. Typography: the rules on spaces, quotation marks and apostrophes specific to French text, handled by deterministic rules rather than by the model.

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