Write a sentence. Get the whole verb.

It comes back in all twelve tenses — positive, negative and question — and anything wrong with what you wrote is named, with the rule it breaks, so you can argue with it rather than take it on faith.

Your sentence One clause, with a subject and a verb. “She writes a letter”, not a paragraph.

Or try one of these — the first is correct, the rest are the mistakes that come up most:

The three it is built around

Tenses — all twelve, what each is for, and why the one you used may be the wrong one for what you meant.
The parts of the sentence — which words are the subject, which are the verb, and what is left, shown on your sentence.
The verb itself — base, he/she/it, past, participle, -ing. Five forms, and nearly every verb mistake is one of them in the wrong place.

Why every correction has a code

V1, A3, P5. Being told a sentence is wrong teaches you that that sentence was wrong. Being told which rule it breaks lets you look it up, disagree with it, and spot the next one yourself — which is the only version that is any use.

It stays on this page

The whole engine runs in your browser. Your sentence is not sent to us or to anybody else, and nothing is stored. Write the thing you are actually unsure about.

The rest of the family

Mathematics Genie does the same for a sum — the working and the reason for each step. Statistics Genie does it for a dataset, checking the assumptions before the p-value.