Is Harper really free?

Yes. Harper is open source: the code is public and installing it costs nothing. At most you pay for hosting if you put it on a server, often a few euros a month. Grammarly Pro, on the other hand, costs €12 a month.

Do I need to code to install Harper?

No. The level is beginner and the install takes about 5 minutes with the prompt from the page: Claude does the work, you answer its questions.

How is it different from Grammarly Pro?

Harper does most of what Grammarly Pro does, without a subscription, and your data stays with you. The point by point comparison is on the page.

Yes. With an open source tool installed on your side, your files stay on your machine or your server. Nobody can close your account or change the price.

Free alternative

Free alternative to Grammarly Pro

Grammarly Pro costs €12 a month. Harper does the same job for free, in open source: you install it on your machine or a small server, and you stop paying.

Public entry price, taken from Grammarly Pro’s website (grammarly.com). Over a year, that is €144 that stays in your pocket.

What replaces Grammarly Pro

The main alternative

Harper

🟢 Beginner⏱️ ~5 min to installSave €12/mo

Harper is Grammarly for English, without the subscription and without sending what you write to the cloud. It underlines spelling, grammar and capitalisation mistakes and clumsy phrasing, in a few milliseconds, right where you write: Chrome, Edge, Firefox, VS Code, Obsidian, WordPress, Neovim, Zed, and a macOS app that checks every text field. Everything happens offline, in Rust, with a memory footprint fifty times smaller than LanguageTool. The project is backed by Automattic, the company behind WordPress: over 15,000 stars, a release every couple of weeks, Apache 2.0 licence. The thing to know before installing: Harper only checks English (American, British, Canadian, Australian, Indian). For your French texts it will do nothing; the core is built for other languages, but none exists yet.

Loucash’s verdict on Harper

8/10

If you write in English and pay for Grammarly, Harper gives you the same basic checking, free, instant, and your text never leaves your machine. That is the argument that matters when you write client emails or internal docs. What I like: the speed (nothing to wait for), the number of places it installs into, and Automattic behind it, the WordPress company: the project will not vanish, it ships a release every couple of weeks. What may bite: it only checks English, full stop. If you mostly write in French, it is not for you. It does not rewrite your sentences either, the way Grammarly Pro does, it corrects. And it can be picky: turn off the rules that annoy you, two clicks.

Who it is for: You write in English every week (clients, content, code) and you want checking without a subscription or your texts leaking. If you only write in French, move along.

See the full page →See the tool ↗

Harper versus Grammarly Pro: the match

Price
Harper
€0
Grammarly Pro
€12 a month billed yearly
Where your text goes
Harper
Nowhere, everything happens offline
Grammarly Pro
To their servers, at every keystroke
Languages
Harper
English only, five variants
Grammarly Pro
English, plus a few languages in beta

Grammarly Pro ↗

VS	Harper	Grammarly Pro ↗
Price	€0	€12 a month billed yearly
Where your text goes	Nowhere, everything happens offline	To their servers, at every keystroke
Languages	English only, five variants	English, plus a few languages in beta
Speed	A few milliseconds, locally	Depends on the network
Where it works	Chrome, Firefox, Edge, VS Code, Obsidian, WordPress, Neovim, Zed, macOS app	Browser, Word, Google Docs, desktop app
AI rewriting	No: it checks, it does not rewrite	Yes, on Pro

The prompt that installs Harper

Paste this prompt into Claude: it checks the repository, asks you its questions and installs the tool step by step.

Je veux installer Harper (correcteur de grammaire anglais open source, dépôt GitHub Automattic/harper, site writewithharper.com) à la place de Grammarly. Demande-moi où j'écris le plus (Chrome, Firefox, Edge, VS Code, Obsidian, WordPress, application macOS) puis guide-moi pas à pas pour installer la bonne extension depuis les liens officiels de la page writewithharper.com/get, et pour la régler : variante d'anglais, règles à désactiver si elles sont trop tatillonnes. Fais-moi taper une phrase avec deux fautes pour vérifier que Harper les souligne. Rappelle-moi qu'il ne corrige que l'anglais, pas le français.

Review the GitHub repository and check whether it is safe to install given my machine and my infrastructure. Ask me as many questions as possible, using widgets, to clarify my request and be as precise as you can.

Frequently asked questions

Is Harper really free?: Yes. Harper is open source: the code is public and installing it costs nothing. At most you pay for hosting if you put it on a server, often a few euros a month. Grammarly Pro, on the other hand, costs €12 a month.
Do I need to code to install Harper?: No. The level is beginner and the install takes about 5 minutes with the prompt from the page: Claude does the work, you answer its questions.
How is it different from Grammarly Pro?: Harper does most of what Grammarly Pro does, without a subscription, and your data stays with you. The point by point comparison is on the page.
Do I own my data?: Yes. With an open source tool installed on your side, your files stay on your machine or your server. Nobody can close your account or change the price.