Grammarly - Clear, effective, mistake-free writing everywhere you type.
Wordtune - AI-powered writing companion
LanguageTool - Free proofreading tool for OpenOffice, LibreOffice, Firefox, and Chrome.
Editsaurus - Highlights potential pitfalls in your writing to encourage good habits.
Anyword - An AI platform for creating effective marketing copy, trained on tens of millions of successful ads.
Gramlee.com - Online grammar check, proofreading and copy editing services.