I've tried other proofreading programs and found them to be very limited. ProWritingAid is the only program I know of that has a built-in grammar checker. Also, the free version has a lot of features that paid versions don't have, so I highly recommend it. This program is great for students who want to improve their writing skills. It's especially helpful for those who write in other languages, because the grammar checker can help you spot errors in your translations.