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February 14, 2025
Digitalization has not stopped at the German language. In addition to the traditional Duden, which has served as a reference work for decades, there are now a number of digital tools that check texts for spelling, grammar, and style. This article compares three of these tools: Duden Mentor, Languagetool, and Deepl Write, and examines their strengths and weaknesses.
Duden Mentor, available online since 2019, offers both a classic and an AI-supported correction mode. In classic mode, the tool impresses with detailed error analysis and well-founded explanations based on the extensive Duden corpus. Particularly helpful are the detailed explanations of grammar rules and the ability to save technical terms in a personal dictionary. The AI integration of Duden Mentor, which runs on Microsoft servers and uses ChatGPT, offers additional functions such as rewriting texts. However, this function is less powerful compared to specialized AI chatbots.
One criticism of Duden Mentor is the limited functionality of the free version, which only checks 500 characters. The premium version, which unlocks features such as the synonym database and browser extensions, is fee-based.
Languagetool, originally an open-source project, offers a solid basic check of spelling and grammar. Compared to Duden Mentor, however, the error analysis is less detailed, and detailed explanations are lacking. Languagetool's AI support provides rewriting suggestions, but these are not always convincing and are sometimes even incorrect. The free version of Languagetool is also limited; the premium version offers extended style checking functions.
Deepl Write, the second product from the well-known translation service Deepl, focuses less on pure error correction and more on rewriting and rephrasing texts. The tool offers comprehensive settings for style, tone, and form of address, allowing texts to be specifically adapted to different target groups. Unlike Duden Mentor and Languagetool, Deepl Write does not provide detailed explanations of the changes made. The free version of Deepl Write uses entered texts to train the AI model, while the paid version refrains from this practice.
The comparison shows that each of the three tools has different strengths and weaknesses. Duden Mentor scores with detailed error analysis and sound explanations, Languagetool offers a solid basic check, and Deepl Write impresses with flexible rewriting options. However, none of the tools can completely replace a human editor. For professional texts, the expertise of an experienced editor is therefore still essential.
