C++ Error: 'std::filesystem' Not Declared: Solution and Explanation

This error occurs when your C++ code lacks the necessary header file for the filesystem library. To fix it, include the following line at the top of your code:

#include <filesystem>

If you're using an older C++ version, you might need the experimental filesystem library:

#include <experimental/filesystem>

Remember that the experimental library isn't universally available across compilers and may have different features compared to the standard filesystem library.