I always forget how to do this one, even though it’s really simple. (Make sure that you have rdoc installed first) To view all the API documentation in gems, simple run:
from the command prompt. It will start a WEBrick server up on your local machine on port 8808. Therefore, if you browse to http://localhost:8808/, you’ll see a list of documentation of the gems on your machine.
It’s incorporated into the gem command now, so just do “gem server”