It will run thin if the gem is installed. Otherwise it falls back to Webrick. Rack itself favours thin, puma, and webrick (in that order). https://github.com/ra

It will run thin if the gem is installed. Otherwise it falls back to Webrick. Rack itself favours thin, puma, and webrick (in that order). https://github.com/rack/rack/blob/6829a8a0f416ea49a18f1e3e532ed1ece24e9ea4/lib/rack/handler.rb#L57 https://github.com/rack/rack/blob/6829a8a0f416ea49a18f1e3e53...