Grammarly - Clear, effective, mistake-free writing everywhere you type.
Wordtune - AI-powered writing companion
LanguageTool - Free proofreading tool for OpenOffice, LibreOffice, Firefox, and Chrome.
Grammatica - AI powered writing assistant
Grammarian PRO3 - Grammarian PRO3 is a feature-rich grammar checker that enables you to write better content without taking assistance from the English teacher.
Linguix Writing Coach - Improve your language skills while writing online