You can do a global code search in Github.com or in your search engine (Google, DuckDuckGo, Bing, whatever). There are some language specific systems like Hoogle [0]. Maybe SourceGraph's global search engine [1] is ok too I have only tried their project-specific views.What is the best hosted/free web app out there today that you use to do searches on code across one or multiple projects?
[0] https://hoogle.haskell.org/
[1] https://sourcegraph.com/search