External documentation can help you learn more about the standard functions, structures, and other items used in your codebase. It opens cppreference.com articles in a browser, or you can use the link in the Quick Documentation popup. The action works for anything with a definition in the std namespace that is likely to have documentation on cppreference.
View cppreference documentation
To open the cppreference page for a symbol at caret, do one of the following:
Press Shift+F1.
Select View | External Documentation from the main menu.
Click the link in the Quick DocumentationCtrl+Q popup:
