ChatGPT grammar checker for drafts

The job

What the ChatGPT grammar checker does

Paste a draft and the ChatGPT grammar checker reads it and tells you what is wrong: agreement, tense, punctuation, dangling modifiers, sentences that lost their subject halfway through. Each finding comes with the reason it is a finding.

It does not send back a corrected document. That is a deliberate choice, and a published side-by-side test of ChatGPT against Grammarly makes the case better than we can: the reviewer got corrected paragraphs back in seconds and had no way to know what the mistakes had been. Grammarly highlighted them. Highlighting is the useful behaviour, so that is the behaviour here.

The workflow

How to check a draft's grammar in three steps

The whole genre of ChatGPT grammar articles is lists of prompts to paste into a chat window. That wrapper is already built here, so step two is the only writing you do.

Step 1

Paste the draft, up to 12,000 characters. Paste whole sections so the checker can see a subject before it judges a verb.

Step 2

Write an instruction of up to 300 characters if you want to steer it: "punctuation only", "explain each mistake", "keep product names".

Step 3

Read the findings and apply what you agree with. Nothing is changed for you, so your document stays yours.

The instruction box

Instructions worth typing into the box

One competitor article is simply ten prompts to paste into ChatGPT, and the list is a good map of what people actually want. Each of these fits in the 300-character field.

"Punctuation only"

A punctuation-only pass. Keeps the check off your word choices when you only wanted commas looked at.

"Explain each mistake simply"

Turns a correction list into a teaching list. This is the single most useful instruction if English is not your first language.

"Focus on articles and prepositions"

Names where your errors actually cluster, which is far more efficient than a general sweep.

"Technical document, check terms are used correctly"

Stops a check flattening specialist vocabulary it does not recognise.

"Business email, flag anything unprofessional"

Register is not grammar, so you have to ask for it explicitly or you will not get it.

"Academic tone"

Asks for the formality problems as well as the errors, which matters more in a submitted paper than a missing comma.

The findings

The grammar mistakes that survive a quick read

Model-drafted text is almost never ungrammatical in an obvious way. These are the errors that read smoothly and are still wrong, which is why a deliberate pass finds things your eye does not.

Agreement across distance

A singular subject, forty words of clauses, then a plural verb pulled in by the nearest noun.

Tense drift

A paragraph opening in past tense and finishing in present, usually switching at a sentence break.

Dangling modifiers

An opening clause that grammatically attaches to the wrong noun, producing a sentence that scans and means something silly.

Comma splices

Two full clauses joined with a comma. Common, fluent and still an error in edited prose.

Orphan pronouns

A sentence starting with "This" when three things in the previous sentence could be the referent.

Duplicated hedges

"May potentially", "could possibly". Two hedges doing one job, which is a habit rather than a rule violation.

What we do not have

What this cannot do that an extension can

Say this plainly so nobody is disappointed after installing nothing. Grammarly's real advantage, as the comparison test put it, is running in real time through a browser extension and giving instant suggestions wherever you are working.

No extension

There is no browser extension and no plugin. Nothing here watches your email client, your docs or your CMS.

No live underlines

Errors are not marked as you type. You run one pass on text you paste in.

No accept button

Nothing rewrites your document. You read the findings and make the edits yourself.

What you get instead

The whole list at once on a finished draft, which catches patterns that a stream of individual underlines never surfaces.

The honest bit

Why it misses things, and why it over-flags

A classic grammar checker applies fixed rules and behaves identically every run. This one is a language model reading your text on our server, which is a different kind of tool with a different failure profile.

Upside: it catches things no rule covers, like a sentence that is perfectly grammatical and impossible to follow. Downside: it can flag a correct but unusual construction, and it can walk past a plain typo. Two runs on the same text will not always return an identical list. So run it twice on anything that matters, and treat a finding as a second reader's opinion you are free to overrule rather than a verdict.

Limits

Length and allowance

Each check accepts between 1 and 12,000 characters, about 1,800 to 2,000 words, which covers most articles, essays and long emails whole. The allowance is 5 free checks per rolling 24 hours, counted from first use rather than resetting at midnight.

Split anything longer at section breaks, never mid-paragraph. Half a sentence gives the checker no subject to test the verb against, and you get a worse report than the text deserves. There is no file upload, so copy the text out of your document first.

Who it's for

Who runs a grammar check before sending

Anyone with one shot at a document: a job application, a client proposal, a piece about to go live. One pass over a finished draft, with the whole list in front of you, beats a week of underlines you dismissed while typing.

Writers working in English as a second language, with the explanation instruction switched on, because a correction that says why is worth more than one that just says what. And editors cleaning up model-drafted copy, where the prose is smooth and the errors are buried in the long sentences.