LanguageTool

A legitimate open-source answer to Grammarly, and the killer feature is that you can self-host the server so your writing never leaves your network, which is exactly what Grammarly can’t offer. The trade is that the free hosted tier checks shorter text and the advanced suggestions push you toward a subscription. For privacy-minded writers the move is clear: self-host the engine if your text is sensitive, or use the free plugins for casual fixes. Choose this over Grammarly whenever you’d rather not feed a US cloud every sentence you type.