I did a Google search to see how to check if a given path is valid, preferably using boost. It brought me here: http://stackoverflow.com/questions/10426671/how-to-check-if-path-is-valid-in... Great! I say to myself. I then Google up the boost doc here: http://www.boost.org/doc/libs/1_62_0/libs/filesystem/doc/portability_guide.h... I then write myself a test: #include <iostream> #include <sstream> #include <boost/filesystem.hpp> int main() { const std::string test1 = "D:\\Programing Projects\\Git Workspace\\Common\\x64\\Debug"; const std::string test2 = "D:\Programing Projects\\Git Workspace\\Common\\x64\\Debug\\"; const std::string test3 = "D:/Programing Projects/Git Workspace/Common/x64/Debug"; const std::string test4 = "D:/Programing Projects/Git Workspace/Common/x64/Debug/"; if (!boost::filesystem::native(test1)) { std::cout << "Boost says the following path is not valid for the native operating system: " << test1 << std::endl; } if (!boost::filesystem::native(test2)) { std::cout << "Boost says the following path is not valid for the native operating system: " << test2 << std::endl; } if (!boost::filesystem::native(test3)) { std::cout << "Boost says the following path is not valid for the native operating system: " << test3 << std::endl; } if (!boost::filesystem::native(test4)) { std::cout << "Boost says the following path is not valid for the native operating system: " << test4 << std::endl; } return 0; } The Test's Output: Boost says the following path is not valid for the native operating system: D:\Programing Projects\Git Workspace\Common\x64\Debug Boost says the following path is not valid for the native operating system: D:Programing Projects\Git Workspace\Common\x64\Debug\ Boost says the following path is not valid for the native operating system: D:/Programing Projects/Git Workspace/Common/x64/Debug Boost says the following path is not valid for the native operating system: D:/Programing Projects/Git Workspace/Common/x64/Debug/ What is wrong with that path that it says it is not valid for my native Windows 10 operating system?