this post was submitted on 25 Nov 2025
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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.

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[–] BlueKey@fedia.io 4 points 2 hours ago (3 children)

How does it compare to Languagetool (which you can also run locally)?

[–] _hovi_@lemmy.world 2 points 46 minutes ago

From the readme:

LanguageTool is great, if you have gigabytes of RAM to spare and are willing to download the ~16GB n-gram dataset. Besides the memory requirements, I found LanguageTool too slow: it would take several seconds to lint even a moderate-size document.

Seems interesting, even if it's still early in development. I'll certainly be trying out the language server in my neovim setup anyway.

Languagetool's browser extension is no longer open source, which has me concerned. You can still point it at a local server, but yeah.

[–] Successful_Try543@feddit.org 4 points 2 hours ago

LT supports also languages other than English, Harper doesn't.

[–] artiman@piefed.social 6 points 3 hours ago (1 children)

very nice ill try switching from languagetool on EU hosted server to this

[–] Successful_Try543@feddit.org 5 points 2 hours ago

FYI: You can also run LanguageTool locally or on your own server.

[–] fubarx@lemmy.world 8 points 4 hours ago

Thanks! Big fan of local and on-device anything.

[–] thatonecoder@lemmy.ca 11 points 5 hours ago

I've used it for 5 months already, at the very least. 9/10, considering how new it is.