Well I have been using Ulysses (mac/ios only) for writing on Medium for pretty much the whole time I've been writing which gives you your word count at the click of a button. But I am switching over to Scrivener (both mac and windows - which gives your word count as you hover over the program search bar, you can also set goals n such).
The thing I found about the Word Counter App I mentioned in the article is that it literally counts every typed word. So if you back space and edit etc. it still counts the previous words - which isn't something I wanted in the end. If you use Word or Google Docs n such there's a way to get the word count without highlighting the whole thing but yeah, either way it's a little more hassle.