I've used it for 5 months already, at the very least. 9/10, considering how new it is.
this post was submitted on 25 Nov 2025
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Do you have a comparison to other tools like Grammarly? Were you sometimes missing suggestions or linting rules?
Haven't used Grammarly in years; however, I can tell you a couple of cons Harper has, compared to Grammarly:
1: It is English-only, for now, although it has all common English dialects
2: It sometimes gets pronunciations of abbreviations wrong, although this is getting less and less common, since the developers work a lot on it
3: There aren't plugins for it on certain editors (e.g. Notepad++), although it has for Chromium/Firefox, VS Code, among others
4: It does lack many style suggestions, but I shall reiterate that they're working on it
Thanks! Big fan of local and on-device anything.
Very nice ill try switching from LanguageTool on EU hosted server to this
FYI: You can also run LanguageTool locally or on your own server.
as an open-source alternative to Grammarly
intentionally avoids including any kind of generative AI in any part of our processing pipeline
Isn't that what Grammarly is all about, though? Be better than traditional spellchecking through LLM?
I assume Harper is entirely Rules based, then? Which inherently means limited to what rules where introduced manually and what the rules cover.
You may like to read @thatonecoder@lemmy.ca's comment, which basically says that they're working on patching these holes.
That comment doesn't say anything about what I'm asking about here.
Fine, then: LLMs hallucinate and make mistakes. You can't beat rules in grammar; get detailed enough and everything will work. My point is that they are actively working on refining rules, which is the best any of us could ask for.
How does it compare to Languagetool (which you can also run locally)?
Languagetool's browser extension is no longer open source, which has me concerned. You can still point it at a local server, but yeah.
Interesting, TIL, thanks. Guess I'll switch...
LT supports also languages other than English, Harper doesn't.
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.