LanguageTool (self-hosted) vs Grammarly
Run the open-source LanguageTool engine (LGPL 2.1+) on your own server, at Hetzner or OVHcloud, and your drafts never leave infrastructure you control. Compared with Grammarly, operated by Superhuman Platform Inc. in San Francisco. Note: the hosted languagetool.org Premium service is operated by US-based Learneo, Inc. and is not an EU alternative.
Your Own Grammar Checker vs Superhuman’s San Francisco Default
This page compares two very different things: running the open-source LanguageTool engine yourself — on your laptop, an internal server, or a VPS at an EU host such as Hetzner or OVHcloud — and Grammarly, the cloud writing assistant operated by Superhuman Platform Inc. in San Francisco.
LanguageTool started in 2003 as Daniel Naber’s open-source project in Germany. The engine is still published under the GNU LGPL 2.1 or later on GitHub, with rule sets for 25+ languages maintained by volunteers and native speakers. You can download it, run it as a small Java HTTP server, and point your browser add-on or LibreOffice at it. Your texts are then checked on hardware you control, and no company sits in between.
An important warning first. The hosted LanguageTool service at languagetool.org — free or Premium — is not an EU alternative. LanguageTool was acquired by Learneo, Inc. in April 2023, and its current terms (effective 21 August 2026) state that the service is owned and operated by Learneo, Inc., a Delaware corporation. Learneo is also the data controller in the privacy policy. If you sign up at languagetool.org, you are using a US service. Everything below concerns the self-hosted open-source engine only.
Grammarly was founded in 2009 in Ukraine by Max Lytvyn, Alex Shevchenko and Dmytro Lider. After acquiring Coda (December 2024) and the email client Superhuman (2025), the parent company renamed itself Superhuman Platform Inc. in October 2025. It is headquartered in San Francisco and hosts the service on AWS in the US East region.
Jurisdiction Comparison
| LanguageTool (self-hosted) | Grammarly | |
|---|---|---|
| Who processes your text | You — on your own server | Superhuman Platform Inc., San Francisco, USA |
| Software origin | Open-source project started in Germany (2003, Daniel Naber) | Founded 2009 in Ukraine (Max Lytvyn, Alex Shevchenko, Dmytro Lider) |
| Licence | LGPL 2.1 or later | Proprietary |
| Hosting location | Wherever you choose (on-premise, Hetzner, OVHcloud, …) | AWS, US East region |
| CLOUD Act exposure | None from the tool — no vendor holds your data | Yes — US company |
| EU transfer basis | Not needed if your server is in the EU | EU-US Data Privacy Framework, SCCs |
| Certifications | Depend on your own hosting | SOC 2 Type 2, ISO 27001, 27017, 27018, 27701, ISO 42001 |
| Hosted languagetool.org service | Operated by Learneo, Inc. (Delaware) — not an EU option | — |
Product Capabilities
What the open-source engine includes
- Rule-based checks for grammar, spelling, punctuation and style in 25+ languages, including English, German, French, Spanish, Dutch, Polish and Portuguese.
- Optional n-gram data (English, German, French, Spanish) that detects commonly confused words; the docs recommend an SSD because the data is large.
- Optional fastText language identification for better automatic language detection.
- An HTTP API that the official browser add-on, LibreOffice and other clients can use.
What is Premium- or cloud-only
- Premium-only rules: the GitHub version is the open-source version without Premium features, as confirmed by LanguageTool co-founder Daniel Naber.
- AI paraphrasing / rephrasing of sentences.
- Synonyms: the server documentation states the local server does not support the add-on’s synonym feature.
- An on-premise Premium licence exists for larger business customers, by quote, but it is contracted with the US-owned company.
Grammarly’s feature set
- Full-sentence rewrites, tone adjustment, fluency suggestions, plagiarism and AI-text detection, and generative AI prompts (100/month free, 2,000/month on Pro, unlimited on Enterprise).
- English-first for 15 years; added French, German, Spanish, Italian and Portuguese in September 2025, and 17 more languages in beta in March 2026.
Notable: for everyday error-catching in European languages, a self-hosted LanguageTool server is genuinely capable. For AI-assisted rewriting in English, Grammarly is in a different league.
Integrations with a local server
- Browser add-on: the official LanguageTool extension can be pointed at your own server (Options → Experimental settings → Local server). Safari requires HTTPS, so you need a reverse proxy.
- LibreOffice 7.4+: built-in LanguageTool Remote Grammar Checker; set the base URL to your server (e.g.
http://localhost:8081/v2) and leave username and API key empty. - Other clients: any tool that speaks the LanguageTool HTTP API can use your server.
- Grammarly: browser extension, Windows and Mac desktop app, mobile keyboard, plus Coda and Superhuman Mail integration — all cloud-only.
Sovereignty Model
- Self-hosted LanguageTool: the strongest model there is — no vendor. The software is LGPL, the server is yours, and the data stays on it. If it runs in your office or with an EU host, GDPR compliance is entirely in your hands and there is no foreign parent in the chain.
- Grammarly: Superhuman Platform Inc. is a US company; CLOUD Act and FISA Section 702 reach apply regardless of where data is stored, and the service is hosted in the US. Users can control in their account settings whether their content trains Superhuman’s AI models.
- Hosted languagetool.org: same structural category as Grammarly — a US controller (Learneo, Inc.) — despite the German team and origins.
Who Self-Hosts It
Typical scenarios (generic, not named customers):
- A law firm, newsroom or public body that drafts confidential text and cannot send it to a US cloud service — one internal LanguageTool server covers all staff
- An IT department that gives every employee the browser add-on and LibreOffice integration, configured to the company server
- A university research group writing papers in a second language, running the server on existing lab infrastructure
- A developer who integrates grammar checking into an internal CMS or documentation pipeline via the HTTP API
- Privacy-minded individuals who run it locally on a laptop or in Docker
Pricing
| LanguageTool (self-hosted) | Grammarly (as of October 2026) | |
|---|---|---|
| Software | Free (LGPL 2.1+) | Free plan: basic checks, 100 AI prompts/month |
| Individual | Your own machine — no cost | Pro: €144/year (€12/month) or €30 monthly, before VAT |
| Team | One shared server for everyone — no per-seat fee | Pro per user; Enterprise by quote |
| Infrastructure | Small VPS or existing server; several GB of SSD per language if using n-grams | Included |
| Operating effort | Updates, TLS, access control | None |
For a team of ten, Grammarly Pro is around €1,440 per year on annual billing. A self-hosted LanguageTool server costs whatever a small EU VPS costs, plus some admin time.
Who Should Switch?
Self-hosted LanguageTool is the right choice for:
- Organisations handling confidential drafts that want zero third-party processing
- Developers and IT teams comfortable running a Java service or Docker container
- Multilingual European teams whose main need is reliable grammar and spelling checks
- Researchers and students who want a free, capable checker for a second language
- Small businesses that want one server for the whole team without per-seat fees
Grammarly remains the better fit for:
- English-first writers who want generative-AI rewriting and tone tools
- Organisations without capacity to run a server
- Enterprises that need vendor-provided SSO, SCIM, audit logs and ISO/SOC reports
The Bottom Line
The hosted languagetool.org service is not a European alternative to Grammarly: since 2023 it has been owned and operated by Learneo, Inc., a US company. But the open-source engine is still LGPL, still actively released, and still runs perfectly well on your own hardware.
Self-hosted LanguageTool gives you something no cloud writing assistant can: grammar checking with no vendor at all. You give up AI paraphrasing, Premium rules and Grammarly’s polished English rewriting, and you take on the job of running a server. For organisations where drafts must stay in-house — and for multilingual Europeans who mostly need solid error-catching — that trade is well worth it.
Looking for more European writing and language tools? See also: DeepL Write vs Grammarly, DeepL vs Google Translate, and LibreOffice vs Microsoft Office.
Frequently Asked Questions
Is the hosted LanguageTool service at languagetool.org a European alternative?
No. LanguageTool began in 2003 as Daniel Naber's open-source project in Germany, and its team still operates from Hamburg (LanguageTooler GmbH). But in April 2023 it was acquired by the US group Learneo, Inc. LanguageTool's current terms (effective 21 August 2026) state that the service is owned and operated by Learneo, Inc., a Delaware corporation in San Francisco, and the privacy policy names Learneo, Inc. as data controller. Texts sent to the hosted service — free or Premium — are therefore handled by a US company and fall within US CLOUD Act reach, just like Grammarly. That is why this page recommends only the self-hosted open-source engine.
What do I get with the self-hosted open-source version?
The LanguageTool HTTP server with the full open-source rule set: grammar, spelling, punctuation and style checks for 25+ languages, plus optional n-gram data for English, German, French and Spanish and optional fastText language detection. You can use it from the official browser add-on (Experimental settings → Local server), LibreOffice's built-in LanguageTool Remote Grammar Checker, or any tool that speaks the LanguageTool HTTP API.
What do I lose compared with LanguageTool Premium or Grammarly?
LanguageTool co-founder Daniel Naber has confirmed that the GitHub version is the open-source version without Premium features. That means no Premium-only rules, no AI paraphrasing, and — according to the server documentation — no synonym feature in the add-on. Compared with Grammarly, you also lose generative-AI rewriting, tone adjustment and plagiarism or AI-text detection. LanguageTool does offer an on-premise Premium licence, but only to larger business customers by quote, and that licence is contracted with the US-owned company.
How hard is it to set up, and what hardware do I need?
The official route: install Java, download the LanguageTool package and start languagetool-server.jar, e.g. on port 8081. By default it only accepts connections from the same machine; add --public and put it behind a reverse proxy with TLS and authentication to serve a team. Community-maintained Docker images (such as erikvl87/languagetool and meyay/languagetool, both updated for LanguageTool 6.8 in 2026) simplify this; the erikvl87 image starts Java with 256 MB minimum and 512 MB maximum heap by default, adjustable via environment variables. If you add n-gram data, plan several GB of SSD storage per language.
Who operates Grammarly and where is my data?
Grammarly is operated by Superhuman Platform Inc. (formerly Grammarly, Inc.), headquartered in San Francisco; the company renamed itself in October 2025 after acquiring Coda and the email client Superhuman. Its terms are governed by California law, its security page states the service runs on AWS in the US East region, and EU transfers rely on the EU-US Data Privacy Framework and standard contractual clauses. Grammarly holds SOC 2 Type 2 and several ISO certifications, but as a US company it is within CLOUD Act reach.
What does it cost?
The self-hosted LanguageTool server is free — you pay only for the machine it runs on, which can be an existing internal server or a small VPS from an EU host. Grammarly Pro costs €12 per user per month billed annually (€144 per year) or €30 on monthly billing, before VAT, as of October 2026; Grammarly Free includes basic checks and 100 AI prompts per month; Enterprise is quote-based.
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