“Your writing assistant”
LanguageTool is primarily an AI editing tool: it improves existing texts with suggestions for grammar, spelling, punctuation, style, tone, and in some cases rephrasing, rather than primarily generating new content like a classic GenAI writer. It is available via web editor, browser, Word, Google Docs, LibreOffice, mail integrations, as well as on Windows/macOS/iOS, and supports more than 30 languages. For developers, there is also an HTTP API and an open-source core technology for self-hosting.
Language Tool
More than a Grammar Checker - Your writing assistant
Origin: Germany ⓘ LanguageTooler GmbH, Boschstraße 23a, 22761 Hamburg, Germany. For the service/data protection context relevant today, Learneo officially states: Learneo, Inc., 2261 Market Street #10569, San Francisco, CA 94114, United States of America
Teams All Premium features plus user management, Team Style Guide, Team Dictionary, and higher text lengths for teams. Other Business DPA available; core functionality open source, own server possible locally or in the cloud; public HTTP API or developer options available.
Target audience
LanguageTool is aimed at people and teams who want to improve existing texts: private users, freelancers, marketing/communications teams, support teams, editorial teams, HR, sales, agencies, and companies with a high volume of written output. LanguageTool is also of interest to developers because the correction logic can be integrated via API or operated independently through the open-source core.
Outstanding features
Particularly strong are the context-aware correction of grammar, spelling, punctuation, style, and tone, multilingual use in 30+ languages, paraphrasing, personal and team style guides, Team Dictionary, the focused editor, as well as broad availability in browsers, Word, Google Docs, LibreOffice, and mail clients. For technical teams, HTTP API, self-hosting, and on-premise are added benefits.
Key use cases
LanguageTool is particularly well suited for proofreading, style improvement, error-free communication, corporate wording, email quality, multilingual text maintenance, and integrating correction mechanics into other software. It is less of a tool for open-ended knowledge research or autonomous workflows, and above all a precise language quality tool.
Usage & notes
What matters is the current product logic: according to the Help Center, the browser extension is Premium-only; free users primarily work via the website. From a data protection perspective, a clear distinction should be made between the website/editor, apps/extensions, business/API, and on-premise, because the data flows differ. A positive point is that LanguageTool officially states that it does not use user inputs to train its language algorithms.
| Target audience | Assessment |
|---|---|
| Private individuals | Very suitable – for spelling, grammar, punctuation, and style in many languages. |
| Self-employed / freelancers | Very suitable – for emails, blog posts, proposals, website copy, and multilingual communication. |
| SMEs / teams | Suitable to very suitable – teams receive Premium features, Style Guide, Team Dictionary, and user management. |
| Developers / privacy-conscious teams | Suitable – the core function is open source and can be operated independently locally or in the cloud. |
| Large enterprises | Conditionally suitable to suitable – Business/DPA available; for Premium on-prem or enterprise features, the specific contractual terms must be reviewed. |
Hosting & Data
1) On-prem / local hosting
Meaning: The company operates the solution on its own hardware or within its own infrastructure. In the strictest sense, not only the application runs locally, but ideally the model as well.
2) Private cloud / data center
Meaning: The solution runs in a dedicated or more clearly separated cloud environment, often with a hosting provider or hyperscaler, but in a German data center or in a particularly controlled environment.
3) EU SaaS / managed
Meaning: The provider operates the solution itself as a service. The company uses the tool as a ready-made cloud service, ideally with EU data residency.
4) Hybrid
Meaning: One part of the processing remains internal / local / in a private cloud, while another part runs in an external cloud or EU SaaS.
5) AVV / DPA
Meaning: This is the data processing agreement or Data Processing Addendum. It governs that the provider processes personal data on behalf of the customer and is bound by the customer's instructions.
6) No training
Meaning: The provider does not use your prompts, uploads, attachments, chat histories, or outputs for training or improving the general model — ideally excluded by contract.
7) Open-source / transparency path
Meaning: There is a path toward greater technical transparency and sovereignty, for example through:
- open models
- documented components
- self-hostable parts
- traceable architecture
- export / switching options
| On-prem / local hosting | ✅ |
| Private cloud / data center | ✅ |
| EU SaaS / Managed | ✅ |
| Hybrid | ⚠️ |
| DPA / AVV | ✅ |
| No training on customer data | ✅ |
| Open source / transparency path | ✅ |
Overall assessment of hosting & data:
LanguageTool can be used both as a cloud writing assistant and via its open-source core functionality. A positive aspect is that anyone can run their own LanguageTool server locally or in the cloud; this is a clear advantage for data protection, offline/private cloud use, and sensitive texts. Also positive are the DPA for business customers, Team Style Guide, Team Dictionary, user management, and the fact that inputs are not used for model training. A critical point is that self-hosting does not automatically cover all premium cloud features and that integrations/clients may work to varying degrees with custom servers.
Conclusion:
Compared to many writing assistants, LanguageTool is particularly attractive for GDPR-oriented setups because self-hosting is possible; however, for full premium features and business use, the DPA, server location, and scope of features should be reviewed specifically.
| On-prem / local hosting | ✅ |
| Private cloud / data center | ✅ |
| EU SaaS / Managed | ✅ |
| Hybrid | ⚠️ |
| DPA / AVV | ✅ |
| No training on customer data | ✅ |
| Open source / transparency path | ✅ |
Overall assessment of hosting & data:
LanguageTool can be used both as a cloud writing assistant and via its open-source core functionality. A positive aspect is that anyone can run their own LanguageTool server locally or in the cloud; this is a clear advantage for data protection, offline/private cloud use, and sensitive texts. Also positive are the DPA for business customers, Team Style Guide, Team Dictionary, user management, and the fact that inputs are not used for model training. A critical point is that self-hosting does not automatically cover all premium cloud features and that integrations/clients may work to varying degrees with custom servers.
Conclusion:
Compared to many writing assistants, LanguageTool is particularly attractive for GDPR-oriented setups because self-hosting is possible; however, for full premium features and business use, the DPA, server location, and scope of features should be reviewed specifically.
Strengths & Weaknesses at a Glance
| Strengths | Weaknesses |
|---|---|
| – Very clear focus on writing, correcting, and improving style. | – Not a full-fledged research or general AI assistant; LanguageTool describes itself more as an AI Editing Tool than an AI Writing Tool. |
| – 30+ languages and dialects, particularly strong in English, German, Spanish, French, Dutch, and Portuguese. | – According to the current Help Center, the browser extension is now only available for Premium. |
| – Many integrations: browser, Word, Google Docs, LibreOffice, mail clients, desktop. | – The practical value increases significantly with Premium; the free version is clearly limited. |
| – Open-source core, self-hosting, and API make the tool unusually flexible. | – Although data protection is comparatively well documented, the current data controller is Learneo, Inc. in the USA, which means international data transfers remain relevant. |
| – Positive for data protection: no use of user inputs for model training, DPA available, on-premise possible. | – According to official communication, language quality and additional checks are more developed in some major languages than in all peripheral languages. |
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GDPR-compliant use possible?
Compared to many GenAI tools, LanguageTool is well documented, but not entirely frictionless.
Positive: DPA pursuant to Art. 28 GDPR, SCCs, reference to the EU-U.S. DPF, no use of user inputs to train the LanguageTool models, editor storage on AWS Germany, API servers according to the API page in Germany and no storage of the transmitted texts there, plus there is an on-premise option without external data transfer.
Limiting: Since 19/12/2024, the responsible data controller for the service has been Learneo, Inc., USA, and the Privacy Policy provides for international transfers. In apps/extensions, certain telemetry/short-term data is also processed; ignored suggestions may contain text fragments, and for acceleration reasons, checks are kept in main memory for up to 15 minutes.
Overall: from a data protection perspective, well defensible for Business/API/On-Prem, but overall only “conditional” because of the US controller/transfers.