DevDocs.io central API Documentation

I found a helpful resource that offers the API of different languages, libraries and frameworks in a standardized form and in one (web-) tool:
https://devdocs.io

Because you can load a selection of APIs into the browser's offline cache, the tool has a very fast response time - even if the web page is not available (e.g. if you are sitting in a lane with a poor Internet connection). If you want to search something in CSS for instance, just enter CSS, press tab and enter the search phrase.

It is really worth to take a look at it. Also take a look into the preferences - it allows to enable a dark theme ;)