Spell - Deep Learning and AI accessible to everyone
Grammarly - Clear, effective, mistake-free writing everywhere you type.
Hunspell - Hunspell is the spell checker of LibreOffice, OpenOffice.
LanguageTool - Free proofreading tool for OpenOffice, LibreOffice, Firefox, and Chrome.
Spell It Out - Spelling out tech acronyms so you can be in the know.
tinySpell - A spell-checker for Windows. Checks text in clipboard and/or on the fly in any Windows program. Small and easy to use. Resides in the taskbar notification area. Free download.