What this grammar checker actually flags
It is a rule list, not a neural editor. It catches doubled words, a/an mix-ups, stray capitals, and a set of common misspellings — then offers a corrected copy you can paste. It will not rewrite tone or invent citations. For sentence-level fog, use the Passive Voice and Flesch tools; for “does this sound like a model wrote it,” use the AI Text Checker.
Run it on emails and short posts before you send. Long academic chapters still want a human pass: subject-verb agreement across clauses is where lightweight checkers go quiet.