Grammar Checker

About the Grammar Checker

Type or paste English text and see its grammar, spelling and punctuation mistakes as you type: subject–verb agreement (“I has”), a and an, repeated words, their and they’re, then and than, its and it’s, missing apostrophes, capitals, word choice (“could of”, “everyday” or “every day”) and hundreds of other rules. Each issue says what is wrong and offers a fix you apply with one click.

Choose the English you write — US, UK, Indian, Australian or Canadian — so spellings such as colour and color are judged the way your readers expect. Words you use that no dictionary knows (names, brands, terms of your field) go into your own dictionary on this device.

The checking is done on your device by Harper, an open-source grammar engine: your text is never uploaded, you don’t need an account, it checks up to a long essay at a time, and it stays fast because nothing waits for a server.

Without a pass you see a free preview: every count of each kind, with the first issues in your text and their fixes. A Pro pass unlocks every issue with its fix.

Common uses

• Proofreading an email, a cover letter or a social post before you send it.
• Checking homework, an essay or a report in the spelling your school or company uses.
• Writing in English as a second language and catching the slips that are easy to miss.
• Checking confidential text — a contract, a medical note — without pasting it into an online service.

What it checks

• Spelling, including the spelling of your chosen English (colour in UK and Indian English, color in US English) and words written apart or together (alot → a lot).
• Grammar: subject–verb agreement, a or an, verb forms and common confusions (their and they’re, then and than).
• Punctuation and capitals: missing apostrophes (dont, isnt), its and it’s, capital letters at the start of sentences and in place names (new delhi → New Delhi).
• Word choice and clarity: could of for could have, everyday for every day, repeated words (the the) and overused phrases such as very unique.

The engine works with rules written by people, not with AI: it does not rewrite your text, it never invents content, and every suggestion comes with the rule’s reason. Like every checker, it can miss a mistake or flag something that is right — you decide.

Your dictionary and ignored issues

Add to dictionary keeps a word on this device (names, brands, technical terms, words of other languages you use in English), so it is never flagged again. Ignore hides an issue for the text you are checking, everywhere it appears. Your dictionary stays in this browser; clear it under the list of issues.

Limitations

• English only. For spelling in French, Spanish, Portuguese or Dutch, use the Spell Checker.
• Up to 100,000 characters (about 15,000 words) are checked at once; a very long text takes a few seconds per check.
• Rule-based checking can miss mistakes, especially in long, complex sentences, and can flag correct sentences; read each suggestion before applying it.
• The first check needs an internet connection to download the engine (16 MB, once).

Privacy

On this device; its files download once

Everything happens in your browser. What you enter or open here is not uploaded or stored by MySmartCoPilot. The first check downloads the grammar engine from MySmartCoPilot once (a 16 MB file, smaller when compressed) and your browser keeps it. Your text is checked on your device and never uploaded.