Grammarly: Free Grammar Checker and Writing Assistant (grammarly.com)
Grammarly makes sure everything you type is easy to read, effective, and mistake-free.
I just installed it and it works perfectly for ASNERS, FB, Wordpress, or any document editor. I'm not saying I am illiterate but sometimes I'm tired, moody, in rush, or just don't care lol This tool makes life super easy when you need to type a lot. Enjoy!