Hemingway - Hemingway App makes your writing bold and clear.
Grammarly - Clear, effective, mistake-free writing everywhere you type.
Ludwig.guru - Linguistic search engine and contextualized translator. The final solution for your writing doubts!
Hunspell - Hunspell is the spell checker of LibreOffice, OpenOffice.
Mate Translate - Ultimate translation app for Mac, iOS, Chrome and many more
GNU Aspell - GNU Aspell, usually called just Aspell, is a free software spell checker designed to replace Ispell.