DevDocs: combines multiple API docs in a fast, and organized interface
devdocs.io
devdocs.io
Not to detract from this, but I can't not give a ringing shoutout / endorsement to Dash[1] in the context of this conversation. If you are on OSX it is just brilliant, and when combined with Alfred[2][3] is just ridiculously seamless to interact with.
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Questions: How did you source the docs? Can they go stale? What versions are being used and is that configurable?