What is the proper way to include an existing external C++ Library into a QT project?

[Bob W]

Do I need to create it as a C++ Library first with QT and then include it into the project, or can I just include the links in the pro file and add the #include file in main?

[koahnig]

The main issue is merely that it has to be in most cases being compiled with the same compiler as your Qt libs. Otherwise you find more details here