{"id":13292,"date":"2026-02-09T09:15:29","date_gmt":"2026-02-09T08:15:29","guid":{"rendered":"https:\/\/www.credativ.de\/?p=13292"},"modified":"2026-05-06T15:11:22","modified_gmt":"2026-05-06T13:11:22","slug":"languagetool-powerful-language-checking-on-your-own-network","status":"publish","type":"post","link":"https:\/\/www.credativ.de\/en\/blog\/credativ-inside\/languagetool-powerful-language-checking-on-your-own-network\/","title":{"rendered":"LanguageTool: Powerful Language Checking on Your Own Network"},"content":{"rendered":"\n
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IMPORTANT NOTE: <\/strong>We have recently been receiving many inquiries regarding the purchase of the premium version of this software mentioned in the article. We do not offer this version and cannot provide assistance with it. As an open-source service provider, we explicitly only handle the open-source version. For questions regarding the commercially distributed product, please contact the manufacturer at https:\/\/languagetool.org\/de<\/a> <\/p>\n<\/div>\n\n\n\n

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LanguageTool: Powerful Language Checking on Your Own Network<\/h2>\n

LanguageTool is one of the leading open-source solutions for grammatical and stylistic text checking. While most users are likely familiar with the cloud-based version, the on-premise (self-hosted) variant is gaining increasing importance \u2013 especially for businesses, educational institutions, and organizations with high data protection and control requirements. <\/p>\n

The core of LanguageTool is licensed under the GNU Lesser General Public License (LGPL-2.1). This license permits the free use, modification, and distribution of the software, even in commercial environments, provided that changes to the original code are also published under the LGPL. The license is “weak copyleft,” meaning that applications using LanguageTool as a library do not necessarily have to be open source. License information can be found in the official repository on GitHub in COPYING.txt<\/a>. Third-party components such as dictionaries may be under different licenses (e.g., GPL). <\/p>\n

There is an open-source version as well as an extended premium version with additional features such as improved style, semantics, and format checks. A detailed overview can be found on the website<\/a>. It is important to note that for self-hosted instances, premium features are only available for commercial use and by individual quote. However, this is communicated with difficulty and primarily in the forum<\/a> upon request. It also appears that not all premium features are available. <\/p>\n

Unfortunately, LanguageTool made changes to the use of browser extensions in 2026: a premium subscription is now required for cloud usage. The self-hosted version remains unaffected \u2013 here, the browser extension can still be connected to your own server to enable seamless integration into web applications such as email, CMS, or forms. <\/p>\n

Features<\/h3>\n

LanguageTool has a modular design and combines several technologies. These go far beyond the integrated spell checking of, for example, LibreOffice or Thunderbird. However, a much-desired feature is currently not yet available: support for multiple languages<\/a> within a single document. <\/p>\n

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    Morphological Analyzer & POS Tagger<\/strong><\/strong>First, the text is broken down into sentences and words. Each word receives at least one Part-of-Speech (POS) tag<\/em> (e.g., noun<\/em>, verb<\/em>, adjective<\/em>). The analyzer also considers inflectional forms, so “gegangen”<\/g> (gone) is correctly identified as a past participle. <\/p>\n<\/li>\n

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    Disambiguator<\/strong><\/em>Many words have multiple meanings (e.g., “Bank”<\/g> as a bench or a financial institution). The disambiguator uses contextual information to select the correct interpretation. This is done either rule-based or statistically and improves the accuracy of subsequent rule application. <\/p>\n<\/li>\n

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    Rule Engine (XML & Java)<\/strong>
    Error detection is based on a combination of:<\/p>\n