LanguageTool — #1 Alternative to Grammarly
Open-source self-hostable multilingual grammar, punctuation, and style server for 30+ languages
Runs privately inside your own Docker container (`erikvl87/languagetool`) while powering browser extensions, LibreOffice, Obsidian, VS Code, and Thunderbird.
License: LGPL-2.1+ · Pricing: Open Core · Compare all Grammarly alternatives · Official Website