Harper – an open-source alternative to Grammarly
39 comments
·June 20, 2025pram
IMO not using LLMs is a big plus in my book. Grammarly has been going downhill since they've been larding it with "AI features," it has become remarkably inconsistent. It will tell me to remove a comma one hour, and then tell me to add it back the next.
boplicity
General purpose LLMs seem to get very confused about punctuation, in my experience. It's one of their big areas of obvious failing. I'm surprised Grammarly would allow this to happen.
chneu
Thank you. In general my grammarly and gboard predictions have become so, so bad over the last year.
raincole
So is there a similar tool but based on an LLM?
Not that I think LLM is always better, but it would be interesting to compare these two approaches.
7thaccount
Grammarly came out before the LLMs. I'm not sure what approach it took, but they're likely feeling a squeeze as LLMs can tell you how to rewrite a sentence to remove passive voice and all that. I doubt the LLMs are as consistent (some comments below show some big issues), but they're free (for now).
demarq
"Me and Jennifer went to have seen the ducks cousin."
No errors detected. So this needs a lot of rule contributions to get to Grammarly level.
alpb
Similarly 0 grammatical errors flagged: "My name John. What your name? What day today?"
null
VTimofeenko
Comes with a great LSP server capable of checking grammar in code comments:
https://writewithharper.com/docs/integrations/language-serve...
icapybara
Why wouldn't you want an LLM for a language learning tool? Language is one of things I would trust an LLM completely on. Have you ever seen ChatGPT make an English mistake?
healsdata
Grammarly is all in on AI and recently started recommended splitting "wasn't" and added the contraction to the word it modified. Example: "truly wasn't" becomes "was trulyn't"
o11c
Hm ... I wonder, is Grammarly also responsible for the flood of contraction of lexical "have" the last few years? It's standard in British English, but outside of poetry it is proscribed in almost all other dialects (which only permit contraction of auxiliary "have").
Even in British I'm not sure how widely they actually use it - do they say "I've a car" and "I haven't a car"?
filterfish
"they" say "I haven't got a car".
Contractions are common in Australian English to, though becoming less so due to the influence of US English.
akdev1l
This is what peak innovation looks like
Groxx
uh. yes? it's far from uncommon, and sometimes it's ludicrously wrong. Grammarly has been getting quite a lot of meme-content lately showing stuff like that.
it is of course mostly very good at it, but it's very far from "trustworthy", and it tends to mirror mistakes you make.
behnamoh
I wish it had keyboard shortcuts. As a Vim user, in Chrome it's tedious to click on every suggestion given by the app. Also, maybe add a "delay" so it doesn't think the currently-being-typed word is a mistake (let me finish typing first!).
Otherwise, it's great work. There should be an option to import/export the correction rules though.
cAtte_
this solution is just fundamentally insufficient. in the age of LLMs it's pretty insane to imagine programmers manually hard-coding an arbitrary subset of grammatical corrections (sure: it's faster, it's local first, but it's not enough). on top of that, English (like any other natural language) is such a complicated beast that you will never write a classic deterministic parser that's sophisticated enough to allow you to reliably implement even the most basic of grammatical corrections (check the other comments for examples). it's just not gonna happen.
i guess it's a nice and lightweight enhancement on top of the good old spellchecker, though
healsdata
Given this is an Automattic product, I'm hesitant to use it. If it gets remotely successful, Matt will ruin it in the name of profit.
josephcsible
It's FOSS, so even if the worst happens, anyone could just fork the last good version and continue development there.
jantissler
Oh, that’s a big no from me then.
null
Looks cool, but it's weird to constantly make comparisons to Grammarly (in the post title, description section of the site, benchmarks) when this is clearly a rule-based spellcheck and very different from what Grammarly offers.
Instead tell me how it compares to the built-in spellcheck in my browser/IDE/word processor/OS.