For the Mac users interested in this, I highly recommend Dash[0], which is an awesome offline alternative and has some ui integration as well. Works on the plane, unlike a website.
Dash has a nice landing page but, after trying it personally a few years ago, didn't care much for its portability or pricing and ended up going with devdocs.io in a pinned tab for the majority of my web development needs.
I have been on the road a lot and with spotty connections, the offline capabilities of Dash are unsurpassed. Also, offline copy of Stackoverflow is golden.
Also I don't really like pages that don't immediately tell me what I get for free and what I will have to pay for. If you will put all your good features behind a paywall, I don't have to waste time downloading a trial. Other way, if you don't tell me I'm going to get pretty much everything I need for free, just with some small limitations, I might not try it, just because I think it's not worth it, without knowing what I get.