A free service that you can use to do a quick check on your writing is Grammarly. Download the free add-on for your browser and it will always be there in the background anytime you are writing on-line. It is not foolproof and it is not right all the time. But, it does check a lot of common errors including misspelled words and punctuation errors.
I use it as an additional backup check for my proofreading and editing. It checks all my Facebook and Twitter posts. It’s even running right now as I write this and caught a few typos from my fumble-fingered hands.
There is also a Word add-on for those who subscribe to the service and online checker that will allow you to cut and paste text from your word processor into an on-line Grammarly window to check for errors.
It will not make you a better writer. But, properly used, it can keep you from making your embarrassing errors public.
And, for people like me, that is a very good thing. 😀