Grammar and spelling checking in the homelab with LanguageTool

Typographical errors noticed only after an email has been sent are a minor but persistent nuisance, particularly when writing in more than one language.

Of the tools I tested, LanguageTool proved the most useful.

It goes beyond spell checking, identifying grammar, style, and contextual issues in more than 30 languages, which is relevant when working in German and English in parallel.

The decisive consideration is that the core of LanguageTool is open source (LGPL 2.1+), so that a self-hosted server can be operated instead of transmitting text to a third-party service.

Deployment via Docker is straightforward and integration proceeds through the HTTP API. The browser extension integrates with Gmail, Outlook on the web, and other sites, so that proofreading occurs in place rather than in a separate application.

The result addresses a practical problem: improved text quality without relinquishing control over the data.