Grammarly - Clear, effective, mistake-free writing everywhere you type.
LanguageTool - Free proofreading tool for OpenOffice, LibreOffice, Firefox, and Chrome.
Gramara - AI grammar correction with transformers
ProWritingAid - For the smarter writer. A grammar checker, style editor, and writing mentor in one package.
Perfect Tense - AI-powered grammar checker with an API
Typosaurus - Quickly check your website for spelling errors