It's Read the Docs - you can switch between versions at the bottom left. Plus more generally it is a pre-1.0 product which, while having a go live licence, mea

It's Read the Docs - you can switch between versions at the bottom left. Plus more generally it is a pre-1.0 product which, while having a go live licence, means it isn't for everyone especially if you're not happy potentially doing some digging through code to work out undocumented features. The OP doesn't say if they are a C# dev or a Ruby dev or neither. To be honest that is likely to be the biggest driver of things. Both are good enough that it isn't really worth paying the price of switching between two ecosystems for.