“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
Location: 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 | ✅ |
On-prem / local hosting: covered
Covered because the website explicitly describes an on-premises/self-hosting option for the core technology. The development page states that anyone can run their own LanguageTool server locally or in the cloud; company documentation also mentions an on-premises version.
Private Cloud / Data Center: Partially
Partially, because EU/German infrastructure and multiple hosting providers are mentioned, but there is no clear description on the website of a dedicated private cloud or isolated customer environment as a standard offering. Controlled operation can be inferred through self-hosting in one’s own cloud.
EU SaaS / Managed: Partially
Partially, because the website mentions EU-relevant hosting locations such as Germany and Ireland, and one PDF even claims that servers are located exclusively in Germany. At the same time, the privacy policy for service use also mentions the U.S., so a purely EU/EEA data residency for the SaaS variant is not consistently documented.
Hybrid: Partially
Partially, because according to the integration document, the widget works with both the cloud and on-premises solutions. This demonstrates technical compatibility, but an explicitly described hybrid operating model with a clear division of processing is not detailed on the website.
DPA: Covered
Covered, because a public DPA/AVV is available and it explicitly states that it meets the mandatory requirements for designating a data processor under Article 28 of the GDPR.
No training: covered
Covered because the privacy policy explicitly states that LanguageTool does not use user input to train its language algorithms or models, and that this is a default setting requiring no opt-out.
Open Source / Transparency Path: Covered
Covered, because the core functionality is described as open source, and the website explicitly allows users to run their own servers locally or in the cloud. This establishes a clear path to transparency and control.
Data Processing
The website presents a mixed picture regarding data processing: There are documented EU-based or German hosting options and a clear self-hosting path, but for standard use, recipients and processing locations in the U.S. are also listed. The DPA lists subprocessors with specific functions, including Telekom Germany, Hetzner, AWS Germany, Google Cloud Platform in Dublin, Cloudflare, as well as OpenAI and Aleph Alpha for rewriting tasks. For transfers outside the EU/EEA, the DPA refers to appropriate transfer mechanisms such as the Data Privacy Framework and Standard Contractual Clauses.
Conclusion
For users in Europe, LanguageTool is generally best evaluated through the on-premises/self-hosting option: This is clearly documented on the website and enables significantly more controllable GDPR-compliant use within EU/EEA infrastructure. The standard SaaS offering is better documented in terms of data protection than many other tools, but due to the explicitly stated connections to the U.S. and the lack of a clear guarantee that data will be stored in the EU as standard, it is not as secure as the self-hosted version.
Sources
- https://languagetool.org/de/legal/dpa
- https://languagetool.org/ru/legal/privacy
- https://languagetool.org/about/
- https://languagetool.org/dev
- https://languagetool.org/pdf/LanguageTool_fuer_Ihr_Unternehmen.pdf
- https://languagetool.org/pdf/LanguageTool_Technischer_Ueberblick.pdf
- https://languagetool.org/pdf/LanguageTool_Integration.pdf
- https://help.languagetool.org/hc/en-us/articles/39254488835095-Does-LanguageTool-offer-an-API
| On-prem / local hosting | ✅ |
| Private cloud / data center | ⚠️ |
| EU SaaS / Managed | ⚠️ |
| Hybrid | ⚠️ |
| DPA / AVV | ✅ |
| No training on customer data | ✅ |
| Open source / transparency path | ✅ |
On-prem / local hosting: covered
Covered because the website explicitly describes an on-premises/self-hosting option for the core technology. The development page states that anyone can run their own LanguageTool server locally or in the cloud; company documentation also mentions an on-premises version.
Private Cloud / Data Center: Partially
Partially, because EU/German infrastructure and multiple hosting providers are mentioned, but there is no clear description on the website of a dedicated private cloud or isolated customer environment as a standard offering. Controlled operation can be inferred through self-hosting in one’s own cloud.
EU SaaS / Managed: Partially
Partially, because the website mentions EU-relevant hosting locations such as Germany and Ireland, and one PDF even claims that servers are located exclusively in Germany. At the same time, the privacy policy for service use also mentions the U.S., so a purely EU/EEA data residency for the SaaS variant is not consistently documented.
Hybrid: Partially
Partially, because according to the integration document, the widget works with both the cloud and on-premises solutions. This demonstrates technical compatibility, but an explicitly described hybrid operating model with a clear division of processing is not detailed on the website.
DPA: Covered
Covered, because a public DPA/AVV is available and it explicitly states that it meets the mandatory requirements for designating a data processor under Article 28 of the GDPR.
No training: covered
Covered because the privacy policy explicitly states that LanguageTool does not use user input to train its language algorithms or models, and that this is a default setting requiring no opt-out.
Open Source / Transparency Path: Covered
Covered, because the core functionality is described as open source, and the website explicitly allows users to run their own servers locally or in the cloud. This establishes a clear path to transparency and control.
Data Processing
The website presents a mixed picture regarding data processing: There are documented EU-based or German hosting options and a clear self-hosting path, but for standard use, recipients and processing locations in the U.S. are also listed. The DPA lists subprocessors with specific functions, including Telekom Germany, Hetzner, AWS Germany, Google Cloud Platform in Dublin, Cloudflare, as well as OpenAI and Aleph Alpha for rewriting tasks. For transfers outside the EU/EEA, the DPA refers to appropriate transfer mechanisms such as the Data Privacy Framework and Standard Contractual Clauses.
Conclusion
For users in Europe, LanguageTool is generally best evaluated through the on-premises/self-hosting option: This is clearly documented on the website and enables significantly more controllable GDPR-compliant use within EU/EEA infrastructure. The standard SaaS offering is better documented in terms of data protection than many other tools, but due to the explicitly stated connections to the U.S. and the lack of a clear guarantee that data will be stored in the EU as standard, it is not as secure as the self-hosted version.
Sources
- https://languagetool.org/de/legal/dpa
- https://languagetool.org/ru/legal/privacy
- https://languagetool.org/about/
- https://languagetool.org/dev
- https://languagetool.org/pdf/LanguageTool_fuer_Ihr_Unternehmen.pdf
- https://languagetool.org/pdf/LanguageTool_Technischer_Ueberblick.pdf
- https://languagetool.org/pdf/LanguageTool_Integration.pdf
- https://help.languagetool.org/hc/en-us/articles/39254488835095-Does-LanguageTool-offer-an-API
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 usage possible?
LanguageTool provides a robust path to GDPR-compliant use within the EU/EEA because it has a Data Processing Agreement (DPA) in accordance with Article 28 of the GDPR and, at the same time, offers a clear self-hosting/on-premises option for its core technology. For the standard SaaS offering, the situation is mixed: The website mentions data flows to the U.S., and the DPA explicitly states that Learneo is a recipient of European data in the U.S. The best available option is therefore on-premise or self-hosting use within the organization’s own or controlled EU/EEA infrastructure.
Positive
Positive aspects include the published T&C/DPA, the documented sub-processors, the reference to the EU GDPR in the DPA, the option to object to changes in subprocessors, the statement that user input is not used to train language algorithms or models, and the openly documented open-source core technology with self-hosted servers. In addition, LanguageTool specifies only servers in Germany and an on-premises version for business documents.
Negative
A negative aspect is that the website for using the service also lists processing locations in Germany, Ireland, and the U.S., and the DPA explicitly describes the receipt of European data in the U.S. by Learneo. A general, clearly guaranteed EU data residency for all SaaS usage within the EU/EEA is not explicitly described on the website as a standard commitment. Certifications such as ISO 27001 or SOC 2 are not listed on the website.
Server Location
The website lists several locations for LanguageTool: in the privacy policy for the use of the services, Germany, the U.S., and Ireland; in the DPA, Telekom Germany, Hetzner, AWS Germany, Google Cloud Platform in Dublin, and Cloudflare in the U.S. are listed as subprocessors, among others. A company PDF also states that LanguageTool uses only servers in Germany; however, this statement appears alongside other information on the website that mentions international processing locations.