[c++] Why is "using namespace std;" considered bad practice?

I think using locally or globally should depend on the application.

Because, when we use the library locally, sometimes the code is going to be a real mess. Readability is going to low.

So, we should use libraries locally only when there is a possibility for conflicts.

I am not a more experienced person. So, let me know if I am wrong.

Examples related to c++

Method Call Chaining; returning a pointer vs a reference? How can I tell if an algorithm is efficient? Difference between opening a file in binary vs text How can compare-and-swap be used for a wait-free mutual exclusion for any shared data structure? Install Qt on Ubuntu #include errors detected in vscode Cannot open include file: 'stdio.h' - Visual Studio Community 2017 - C++ Error How to fix the error "Windows SDK version 8.1" was not found? Visual Studio 2017 errors on standard headers How do I check if a Key is pressed on C++

Examples related to namespaces

Class 'App\Http\Controllers\DB' not found and I also cannot use a new Model How do I get an object's unqualified (short) class name? socket.error:[errno 99] cannot assign requested address and namespace in python What is the use of "using namespace std"? Visibility of global variables in imported modules Using :: in C++ 'namespace' but is used like a 'type' type object 'datetime.datetime' has no attribute 'datetime' Why am I getting error CS0246: The type or namespace name could not be found? string in namespace std does not name a type

Examples related to std

Converting std::__cxx11::string to std::string What is the use of "using namespace std"? How to get error message when ifstream open fails How to declare std::unique_ptr and what is the use of it? declaring a priority_queue in c++ with a custom comparator cc1plus: error: unrecognized command line option "-std=c++11" with g++ How to convert std::chrono::time_point to calendar datetime string with fractional seconds? string in namespace std does not name a type cout is not a member of std printf with std::string?

Examples related to using-directives

The type or namespace name could not be found The type or namespace cannot be found (are you missing a using directive or an assembly reference?) Why is "using namespace std;" considered bad practice?

Examples related to c++-faq

What are the new features in C++17? Why should I use a pointer rather than the object itself? Why is enum class preferred over plain enum? gcc/g++: "No such file or directory" What is an undefined reference/unresolved external symbol error and how do I fix it? When is std::weak_ptr useful? What XML parser should I use in C++? What is a lambda expression in C++11? Why should C++ programmers minimize use of 'new'? Iterator invalidation rules