Grammarly Chrome Extension

I've always been pretty good at spelling so built-in spell checkers don't catch a lot more that I do, but grammar is a bit more of the challenge, and that's where I find this Google Chrome extension very useful.  The free version does everything I need it to do, but there are paid enhancements for the more professional user.

https://chrome.google.com/webstore/detail/grammarly-for-chrome/kbfnbcaeplbcioakkpcpgfkobkghlhen?hl=en