Fantastic work, I was so fed up with Grammarly and instantly installed this.

I'm just a bit skeptical about this quote:

> Harper takes advantage of decades of natural language research to analyze exactly how your words come together.

But it's just a rather small collection of hard-coded rules:

https://docs.rs/harper-core/latest/harper_core/linting/trait...

Where did the decades of classical NLP go? No gold-standard resources like WordNet? No statistical methods?

There's nothing wrong with this, the solution is a good pragmatic choice. It's just interesting how our collective consciousness of expansive scientific fields can be so thoroughly purged when a new paradigm arises.

LLMs have completely overshadowed ML NLP methods from 10 years ago, and they themselves replaced decades statistical NLP work, which also replaced another few decades of symbolic grammar-based NLP work.

Progress is good, but it's important not to forget all those hard-earned lessons, it can sometimes be a real superpower to be able to leverage that old toolbox in modern contexts. In many ways, we had much more advanced methods in the 60s for solving this problem than what Harper is doing here by naively reinventing the wheel.

Harper is decent.

I've relied on Grammarly to spellcheck all my writing for a few years (dyslexia prevents me from seeing the errors even when reading it 10 times). However, I find its increasing focus on LLMs and its insistence on rewriting sentences in more verbose ways bothers me a lot. (It removes personality and makes human-written text read like AI text.)

So I've tried out alternatives, and Harper is the closest I've found at the moment... but i still feel like grammarly does a better job at the basic word suggestion.

Really, all I wish for is a spellcheck that can use the context of the sentence to suggest words. Most ordinary dictionary spellchecks can pick the wrong word because it's syntactically closer. They may replace "though" with "thought" because I wrote "thougt" when the sentence clearly indicates "though" is correct; and I see no difference visually between any of the three words.

I would much rather check my writing against grammatical rules that are hard coded in an open source program—meaning that I can change them—than ones that I imagine would be subject to prompt fiddling or worse; implicitly hard coded in a tangle of training data that the LLM would draw from.

The Neovim configuration for the LSP looks neat: https://writewithharper.com/docs/integrations/neovim

The whole thing seems cool. Automattic should mention this on their homepage. Tools like this are the future of something.

LanguageTool (a Grammarly competitor) is also open source and can be managed locally:

https://github.com/languagetool-org/languagetool

I generally run it in a Docker container on my local machine:

https://hub.docker.com/r/erikvl87/languagetool

I haven't messed with Harper closely but I am aware of its existence. It's nice to have options, though.

It would sure be nice if the Harper website made clear that one of the two competitors it compares itself to can also be run locally.

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.

"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.

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.

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?

Harper was acquired by Automattic in January 2025

https://automattic.com/2024/11/21/automattic-welcomes-harper...

Surprised coming into this that I don't see anyone mentioning vale[0]. I've been using it for ~4 years now and love it.

I use grammarly briefly when it came out and liked the idea. Admittedly it has more polish than vale for people writing in google docs, &c. Still, I stick with Vale. Is there any case for moving to Harper?

[0] https://vale.sh/

Would be nice if they had a website where you could demo/test it before downloading extensions and stuff. Their firefox extension opens to this page https://writewithharper.com/install-browser-extension but when you paste in anything more than a few paragraphs the highlighting is all messed up.

Comes with a great LSP server capable of checking grammar in code comments:

https://writewithharper.com/docs/integrations/language-serve...

Seeing Harper as an implementation of natural language's LSP brings me great joy, as it proves an idea I've had for a long time—natural language and programming languages are interconnected. Many concepts and techniques from programming languages can also be applied to natural language, making our lives more convenient. The development of LLMs and vibe coding has further blurred the boundary between natural language and programming languages, offering similar insights.

Great to hear

i honestly don't trust grammarly ... i mean, its essentially a keylogger.

i did try it a bit once, and i never seem to have it work that well for me. But i am multilingual so maybe thats part of my hurdle

I'm a long-time Grammarly user. I just tried Harper, and it simply performs very poorly. It is a good initiative, but I don't feel the current state of this software to be worthwhile.

Any chance to make the obsidian plugin work in mobile/Android?

Looks very good. Was looking to replace ltex (which is really slow), but for some reason the nvim-lspconfig filetype setting for harper doesn't seem to have (la)tex listed as a default, although markdown and typst are listed. Anyone knows why?

Slightly controversial compared to other comments here but I haven't used Grammerly at all since LLMs came out. Even a 4B local LLM is good enough to rephrase all forms of text and fix most grammer mistakes.

In a world of LLMs, it's great to see classic NLP works like Harper. Both definitely have their own use cases.

“Yo who dis?”

Passes.

For reference: https://youtu.be/w-R_Rak8Tys?si=h3zFCq2kyzYNRXBI

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.

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

I don't understand why we even need such services. Why don't the browsers and maybe even the OS just not improve their included grammar checkers?

The Chrome enhanced grammar checker is still awful after decades.

Maybe the AI hype will finally fix this? I'm still surprised this wasn't the first thing they did.

Odd choice that the example text on the homepage is almost all obvious typos that a standard spell check would pick up.

My biggest problem with Grammarly has always been how buggy the product is. From not checking random sites to messing up formatting to not updating text with the selected changes.

If Harper does better at this I’d change in a minute.

this is the right direction. rulebased, local, transparent. not perfect yet, but that's not the point. getting something lightweight and tweakable matters more than catching every edge case out of the box. if it misses, you add rules. simple as that. if you expect it to match grammarly day one then might be we are missing the tradeoff

Unfortunately, the last time I tested Harper inside Neovim, it alone used more than 1 GB of RAM for just the LSP! However, the concept is nice, open source, no AI, and easy to integrate.

Any chance to get it working in word? my wife would love to use it most likely

Very cool. Has anyone integrated this into their own app? How was your experience?

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.

It is available in Autommatic's Github repository:

https://github.com/Automattic/harper

Are languages other than English also supported? Or is this for English only?

"For most documents, Harper can serve up suggestions in under 10ms." 10l is OK. 10kg as well. Why is 10ms wrong?

Looks awesome! I’ll give it a try over language tool.

Is there any reason why there is no firefox extension?

Who is the target market is for Grammarly? Working professionals who speak English as a second language?

Very buggy, but great start!!

I.e. if you write an "MISTAEK" and then you scroll the highlight follows me around the page

I think if you can self host language tool, it would still be the better option.

nice name!

This seems to use a hard coded list of explicit rules, not an LLM

https://writewithharper.com/docs/rules

https://github.com/Automattic/harper/blob/0c04291bfec25d0e93...

        "PointIsMoot" => (
            ["your point is mute"],
            ["your point is moot"],
            "Did you mean `your point is moot`?",
            "Typo: `moot` (meaning debatable) is correct rather than `mute`."
        ),

I used to see ads for Grammarly and wondered if anyone was using it.

Then post COVID with the increase in screen sharing video calls, I soon realised nearly every non-native English speaker from countries around the world heavily relied on it in their jobs. As I could see it installed when people share screens.

Huge market, good luck.

Good start. But still has bugs i guess.

I tried with the following phrase -- "This should can't logic be done me." --

No errors.

Is this using local LLMs or some other engine?

No serial comma? Screw that.

Great! Please create an iOS keyboard with Harper

vim plug?

Which LLM is running with Harper?

I never understood the appeal of grammar tools. If you have reached the minimum professional/academic level needed to be designated to write something, shouldn't you at least be capable of verifying its semantic "correctness" just by reading through it once yourself?

Why would you pass a writing job to someone who isn't 100% fluent in the language and then make up for it by buying complex tools?