Language Tool
Open-source proofreading software that checks grammar, style, and spelling in many languages.
Open the official app on languagetool.org
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Use it free
Open the official tool or demo — no account needed.
Self-host it
Run the open-source version on your own infrastructure.
What is Language Tool?
LanguageTool is an open-source grammar, spelling, and style-checking tool designed to identify errors in text across 25+ languages. It serves as a free alternative to commercial writing assistants, offering automated corrections for grammatical structures, punctuation, and vocabulary usage. Widely adopted by organizations such as the European Union, Deutsche Presse-Agentur, and JetBrains, it addresses common writing challenges faced by professionals, students, and multilingual authors. The tool resolves issues like subject-verb agreement, incorrect prepositions, and inconsistent verb tenses, while also supporting advanced features like style suggestions and punctuation refinement. Its modular design allows customization for specific industries or linguistic contexts, making it a versatile solution for improving clarity and correctness in written communication.
How it works
LanguageTool is a free, open-source project that combines rule-based and AI-driven methods to detect and correct errors in text. It supports over 25 languages, including German, English, French, and Spanish, and is used by both individuals and organizations to enhance writing quality. The tool automates the process of identifying grammatical mistakes, spelling errors, and stylistic inconsistencies. Its primary purpose is to assist writers in producing more accurate and polished content without requiring extensive linguistic expertise. LanguageTool excels at detecting subject-verb agreement errors, incorrect prepositions, and misplaced modifiers. For example, it can flag 'The meeting was attended by me and he' as incorrect and suggest 'The meeting was attended by me and him.' It also handles punctuation issues, such as missing commas in complex sentences, and offers style suggestions for varying tone and formality levels.
How to use it
- 1Open the Language Tool page
- 2Use the tool directly in your browser
- 3Results appear instantly — no waiting, no downloads
What it can do
- grammar checker
Use cases
Assumptions and limitations
Assumptions
- source: https://github.com/languagetool-org/languagetool
- license: LGPL-2.1 — free to use
- privacy: Self-hosted — you control your data
Limitations
- Rule-based checks may miss context-dependent errors requiring deeper semantic analysis
- AI-driven suggestions occasionally produce false positives in idiomatic expressions
- Limited support for highly specialized jargon in niche fields like medicine or law
- The free version lacks advanced features like plagiarism detection available in premium tools
- Real-time browser add-on functionality is restricted to basic grammar checks
Understanding the result
Open-source proofreading software that checks grammar, style, and spelling in many languages.
Tool details
- Clearly flagged when a network request is needed.
- No account, no sign-up, and no tracking of your content.
- Powered by (MIT).
- Built with
- (languagetool-org/languagetool)
- License
- MIT
- Runs locally
- No — requires a network request
- Verification
- Not yet verified
- Input
- Query
- Output
- Text
Built with languagetool-org/languagetool. OpenToolVault provides the discovery and browser interface while crediting the original project maintainers.
- Built with
- License
- MIT
Open-source project
OpenToolVault is an independent directory. We are not affiliated with or endorsed by this project.
References
- / — GitHub Repository
Upstream project · GitHub
- LGPL-2.1 License
Upstream project
Frequently asked
How does LanguageTool handle different languages?
LanguageTool uses language-specific rule sets and dictionaries for each supported language. These rules are continuously updated by a community of contributors. The tool automatically detects the language of the input text, though users can manually select a language for more precise results. For less common languages, additional rule files may be required to ensure accurate error detection.
What technologies power LanguageTool's grammar checking?
The tool combines rule-based grammar checking with machine learning models trained on extensive text corpora. Rule-based systems analyze syntax and structure using predefined linguistic patterns, while machine learning components identify common error types through statistical analysis of writing samples. This hybrid approach allows LanguageTool to balance precision with adaptability across diverse linguistic contexts.
How can I check a document for grammar errors?
To check a document, paste the text into the LanguageTool editor on their website or use the browser add-on. Select the target language, then click 'Check' to receive inline suggestions. For documents with complex formatting, use the desktop application to preserve layout while performing checks. Review the highlighted errors and apply suggested corrections directly within the interface.
How does LanguageTool compare to Grammarly?
LanguageTool offers broader language support (25+ languages) and open-source transparency, while Grammarly focuses on English with more advanced AI-driven suggestions. LanguageTool's rule-based system provides precise control over linguistic norms, whereas Grammarly's AI prioritizes natural-sounding corrections. Both tools have premium versions, but LanguageTool's free tier includes more comprehensive features for non-English writing.
What should I do if LanguageTool flags a correct sentence as an error?
If a valid sentence is incorrectly flagged, add it to your personal dictionary to prevent future false positives. For complex errors, consult the tool's rule configuration files to adjust or add custom rules. Community forums and issue trackers can also help identify and resolve specific false positives in the tool's rule sets.