LanguageTool is a multilingual grammar, style, and spell checker offered as a web editor, browser add-ons, e-mail and office plugins, desktop and iOS apps, and a paid Premium tier. Its open-source core (LGPL 2.1, started by Daniel Naber in 2003) can be self-hosted, but the hosted service — the default for all official apps and add-ons — sends the text a user types to LanguageTool's servers for checking. The service is operated by LanguageTooler GmbH (Hamburg, HRB 198018), which since an April 2023 acquisition is a subsidiary of Learneo, Inc., the privately held Delaware/California parent of Course Hero, QuillBot, Scribbr, and others; the current terms name Learneo as owner and operator and the privacy policy names Learneo as data controller. The operator states that texts checked through the browser add-on are 'usually not saved', that the add-on stores no IP address and needs no account, and that LanguageTool inputs are not used to train models by default; texts written in the online editor or desktop apps are stored (on AWS per the business DPA), and the optional rephrasing feature sends text to OpenAI or Aleph Alpha. The unified Learneo privacy policy (a preview effective August 21, 2026 was live at drafting time) discloses Google Analytics, Amplitude, session-replay tools (Fullstory, Microsoft Clarity), interest-based advertising, and that browser-extension 'Content' may include the content of websites visited. No breach, regulatory action, or independent audit involving LanguageTool was found in this research.
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LanguageTool's Premium page FAQ states that texts written using the browser add-on are 'usually not saved', that only texts in the online editor are saved (so they can be accessed across devices), and that LanguageTool can be used without a user account in browsers and word processors — the operator's own hedged retention statement for the core checking function.
The Firefox add-on listing (published by LanguageTooler GmbH, ~331,000 users) shows the required permission 'Access your data for all websites' and states that by default text is sent to languagetool.org over an encrypted connection, that no account is needed, and that the IP address is not stored; the extension itself is listed as 'All Rights Reserved' (proprietary), unlike the LGPL core.
The Learneo, Inc. privacy policy that governs LanguageTool (a preview effective August 21, 2026 was live at drafting; the prior version applies until then) states that it collects all Content a user inputs, and that for browser extensions Content 'may include the content and metadata of all websites you're visiting during your active browser session'; it also lists account data and payment processors (Adyen, Amazon Pay, Stripe, PayPal, Chargebee, Razorpay, Google Pay, EBANX, Apple Pay) for paid plans.
LanguageTool's imprint names LanguageTooler GmbH, Boschstraße 23a, 22761 Hamburg, registered at Amtsgericht Hamburg HRB 198018, with managing directors Stephen Van Horne and Jennifer Seidel and VAT ID DE315084345, and discloses funding from the European Union / European Regional Development Fund and the European Social Fund via Brandenburg's labour ministry.
The LanguageTool GitHub README states the core is open-source proofreading software available under the LGPL 2.1 or later and links instructions for running your own LanguageTool server — meaning the text-checking engine (without the cloud-only AI rules) can be self-hosted so text never leaves the user's infrastructure.
On April 5, 2023, Learneo, Inc. announced its acquisition of German-founded LanguageTool, describing founder Daniel Naber's 2003 open-source start, co-founder Christopher Blum, over 60,000 paying subscribers, and Learneo's seven business lines (CliffsNotes, Course Hero, LanguageTool, LitCharts, QuillBot, Scribbr, Symbolab); Learneo is privately held and the announcement discloses no purchase price or investors.
LanguageTool's business Data Processing Agreement (last modified August 21, 2024) names Learneo as 'the Processor and owner of LanguageTool' receiving European data in the US, and publishes a subprocessor list: Telekom Germany and Hetzner (hosting the text-checking servers), AWS EMEA Germany branch (database for access data and usage logs, and storage of texts written in the online editor or desktop apps), Cloudflare, Google Cloud, Amplitude (analytics), LanguageTooler GmbH (local affiliate), and OpenAI LLC and Aleph Alpha GmbH used only for the rephrasing feature.
The LanguageTool General Terms and Conditions (effective August 21, 2026) state that LanguageTool is owned and operated by Learneo, Inc., a Delaware corporation, and grant Learneo a license over User Content limited to providing the service, complying with law, and enforcing policies, adding that User Content is not used to train its AI models.
Privacy Guides lists LanguageTool on its Language Tools page under criteria requiring that tools be open source and self-hostable, noting the operator's statement that submitted content is not stored while pointing to self-hosting for higher assurance.
LanguageTool's own December 2024 terms-and-privacy update notice states that LanguageTool is now managed by Learneo, Inc. as the responsible company and that, as a product change, customer inputs are no longer used to train its language models by default — a documented, user-favorable policy change, though not a third-party audit, transparency report, or bounty program.
The App Store privacy label for the LanguageTool iOS app (seller LanguageTooler GmbH) declares Contact Info (email, name) as data linked to the user, and Usage Data (product interaction), Diagnostics, and User Content (emails or text messages) as data not linked to the user — analytics collection is declared but no advertising or tracking category is listed.
The LanguageTooler cookie policy (last updated November 25, 2024, 'a Learneo, Inc. service') describes analytics and advertising/retargeting cookies, says non-essential cookies are consent-gated via OneTrust for EEA, UK and Canada residents, and states that the service does not support Do Not Track requests.
The Learneo privacy policy governing LanguageTool discloses Google Analytics and Amplitude analytics, session-replay tools from Fullstory, Amplitude and Microsoft (Clarity) that record mouse movements and keystrokes, and interest-based advertising and retargeting; its cookie section also lists fingerprinting and device-recognition technologies among the tracking methods used.