LanguageTool is an open-source grammar, style and spell-checking tool that has been refined since 2003, and it stands out for one thing above all: genuinely deep multilingual support. It covers more than 30 languages and dialects — English, German, French, Spanish, Portuguese, Dutch, Polish, Russian and many more — and, unlike competitors that treat non-English languages as a superficial afterthought, it provides thorough, native-quality checking for each, backed by thousands of language-specific rules built and maintained by professional linguists and an active open-source community. If you write in more than one language, that depth is unmatched.

The right way to judge LanguageTool is as a precise, multilingual, privacy-conscious proofreader rather than a content-generation suite. On that measure it’s excellent — accurate, affordable and uniquely respectful of your data — with a few rough edges around interface polish and AI extras. Here’s the honest picture.

What LanguageTool does

Grammar and style across 30+ languages

At its core, LanguageTool spots and corrects grammar mistakes, spelling errors and punctuation problems, then layers on style suggestions to improve readability. What makes it special is the multilingual depth: it detects commonly confused words in context, flags “false friends” between languages for people writing in a second tongue, and identifies register mismatches where formal and informal language are inappropriately mixed. For non-native writers, it’s frequently described as the best proofreading tool available.

Picky Mode, paraphrasing and personal dictionary

The Premium version adds advanced style suggestions and a Picky Mode for refined, polished writing, plus word-frequency analysis to catch repetition and an extended personal dictionary. There’s also AI-powered paraphrasing that suggests clearer or more concise alternative phrasings for whole sentences. It’s a focused toolkit aimed at making your existing writing better rather than generating new content from scratch.

Works everywhere, with an open-source core

LanguageTool runs as a browser extension for Chrome, Firefox, Safari and Edge, with dedicated add-ins for Microsoft Word, Google Docs, LibreOffice and Apple Mail, plus a full web editor — and it works across most websites including Gmail, social platforms and LinkedIn, showing blue underlines you click to fix. Crucially, the core engine is fully open source under the LGPL, with EU-based data processing, and an enterprise API lets developers embed multilingual checking into their own applications.

How LanguageTool scores

Overall score: 8.0 / 10, the average of the eight categories above.

LanguageTool pricing

LanguageTool is one of the most affordable comprehensive grammar tools available — roughly a third of Grammarly’s annual cost — with a solid free tier and a self-hosting escape hatch for the privacy-conscious. Confirm current figures on the site.

At about $4.99/month, Premium is exceptional value, and the free tier alone outperforms many paid competitors for basic checking. For organisations needing the strongest compliance posture, the open-source self-host option is a genuine advantage no other major grammar checker offers.

Where it falls short

Less polished than consumer rivals

LanguageTool’s interface is functional rather than slick, and it can feel a step behind consumer-first tools like Grammarly in presentation and onboarding. It also tends to struggle with very long texts, where checking can slow or feel less thorough than on shorter pieces. For most everyday writing this is a non-issue, but if you want the most refined experience or routinely edit book-length documents, it’s worth bearing in mind.

Hosted data leaves the EU unless you self-host

The privacy story has a nuance worth knowing. The hosted service is run by Learneo and processes data under GDPR with EU-based handling, but personal data may be transferred outside Germany under standard legal frameworks — the same basis many US-owned SaaS products use. For most users that’s perfectly acceptable; for those needing a fully sovereign stack, the open-source self-host option removes cross-border transfers entirely. Choose the deployment that matches your compliance needs.

Pros and cons

Who should use LanguageTool?

LanguageTool is for anyone who writes in more than one language, for privacy-conscious individuals and organisations, and for cost-sensitive writers who want premium-grade checking without Grammarly’s price. If you draft in English plus another language, value the option to self-host, or simply want accurate grammar checking for around $5 a month, it’s the clear choice — and developers gain a genuinely capable multilingual API to build on.

If you write only in English and want the most polished inline experience, Grammarly edges it; for deep style analysis and authoring, ProWritingAid goes further; for heavy paraphrasing, QuillBot leads; and for raw AI writing, ChatGPT.

Verdict

LanguageTool occupies a position no rival can quite match: genuine multilingual depth across 30-plus languages, an open-source core you can self-host, EU-based data processing and a price around a third of Grammarly’s. For multilingual writers it’s simply the best proofreader available, and for privacy-conscious teams the self-hosting option is a decisive advantage. Even the free tier outperforms many paid competitors on basic checking.

It’s held back by a less-polished interface, weaker performance on very long texts, lighter AI paraphrasing and limited plagiarism checking — reminders that it’s a focused proofreader rather than an all-in-one writing suite. Judge it on what it sets out to do — accurate, affordable, multilingual, private grammar checking — and it’s outstanding. Know your priorities and it may well be the smartest-value writing tool you can buy. Score: 8.0/10.

Frequently asked questions