Harper: Free, Open Source Grammar Checker

What is it?

Harper is a free English grammar checker designed to be just right. You can think of it as an open-source alternative to Grammarly. I created it after years of dealing with the shortcomings of the competition.

Private

Harper is completely private, in every sense of the word.

Since Harper runs on-device, your data doesn't go anywhere you don't want it to.

That means you have 100% certainty we don't violate your copyright by training large language models.

Harper also intentionally avoids including any kind of generative AI in any part of our processing pipeline.