A private grammar checker that works in your browser
This grammar checker finds spelling mistakes, grammar errors, punctuation problems and clumsy style in your writing, explains each one in plain words and fixes it with one click. Choose US, UK, Australian, Canadian or Indian English, and it checks spellings such as colour, realise and centre the way your readers expect.
The checking is done by Harper, an open-source grammar engine made by Automattic (Apache-2.0 licence), compiled to WebAssembly and run in a background thread of your browser. Your text is never uploaded — useful for job applications, client emails, school work and anything confidential. The engine downloads once (about 8 MB) and your browser keeps it.
Names and specialist words you use often can be added to your own dictionary, false alarms can be ignored, and an optional AI rewrite — using your browser’s built-in AI or a small open model on your device — suggests a corrected version of a whole sentence.
How to check your grammar
- Paste or type your text into Your text.
- Pick your English variant — US, UK, Australia, Canada or India.
- Press Check grammar. The first time, the grammar engine downloads; after that, checking is instant and updates as you type.
- Read the underlined words and the issue list. Click a suggestion to fix it, Ignore to dismiss it, or Add to dictionary for a correct name or term.
- Use Undo fix if a change was wrong, then Copy text when you are done.
Grammar Checker features
Grammar, spelling, punctuation, style
Issues are grouped in four colours with counts, so you can work through spelling first or hide style hints.
Five English variants
US, UK, Australian, Canadian and Indian English, as supported by Harper 2.10.0.
One-click fixes and undo
Each issue lists Harper’s suggestions; the change is applied to your text and checked again.
Your own dictionary
Add names such as “Priyanka” once; the list is kept in this browser and used on every check.
Optional AI sentence rewrite
For a tangled sentence, ask an on-device model for a corrected version and compare before using it.
Works without a server
Harper runs in a Web Worker; if WebAssembly is blocked, this page’s own basic rules still catch common mistakes.
What it catches — an example
Checking “This is an test. I has a apple and their going too the store. The the cat sat on the mat. i like it. We should of known. Its a nice day, isnt it?” in US English gives nine issues:
| Text | Suggestion | Type |
|---|---|---|
| an test | a test | Grammar (article) |
| I has | I have | Grammar (agreement) |
| a apple | an apple | Grammar (article) |
| going too the store | to | Grammar (word choice) |
| The the cat | The | Style (repetition) |
| i like it | I | Punctuation (capitalisation) |
| should of known | should have | Grammar (word choice) |
| Its a nice day | It’s | Punctuation |
| isnt | isn’t | Spelling |
Limits of automatic grammar checking
- No checker understands meaning. In the same example, “their going” is not flagged — read your text once more after fixing the marked issues.
- Names, brands and technical terms are often unknown words; add the correct ones to your dictionary.
- Style suggestions are opinions. Ignore them when the original says what you mean.
- Harper checks English only. For other languages, the Language Detector tells you what you have, and the Translation Tool can translate it.
US, UK and Indian English spelling
Choose the variant your readers use. In US English, the sentence “We realised the colour of the centre was grey” gets four spelling issues; in UK or Indian English it gets none. For a final polish, check sentence length with the Readability Checker or reword with the Paraphrasing Tool.
| US English | UK, Australian and Indian English |
|---|---|
| color, favor, honor | colour, favour, honour |
| center, theater | centre, theatre |
| realize, organize | realise, organise (Oxford-style UK English also accepts -ize) |
| gray, check (payment) | grey, cheque |
Grammar Checker FAQ
Is this grammar checker free and private?
Yes. It is free, needs no account, and checks your text inside your browser. Only the grammar engine itself is downloaded; your writing never leaves your device.
Which grammar engine does it use?
Harper 2.10.0 by Automattic, an open-source checker written in Rust and released under the Apache-2.0 licence. Its word list comes from the SCOWL-based Hunspell dictionaries, which have a permissive licence.
Does it support British and Indian English?
Yes. Choose English (UK), (Australia), (Canada) or (India) and spellings like colour, centre and realise are accepted.
Why is a correct name marked as a spelling mistake?
The dictionary does not know every name. Press Add to dictionary and it is accepted from then on in this browser.
Does it work offline?
After the first check the engine is in your browser’s cache, so it keeps working while the cache lasts. If the engine cannot load at all, basic checks from this page still run.
Can it rewrite a whole sentence?
Yes — press Rewrite sentence on an issue and run the optional AI rewrite. It uses your browser’s built-in AI or an open model on your device after you agree to the download.