How to add include path in Qt Creator?

I have a project I'm working on in Qt creator that requires a third-party library. I want to add the headers to the include path for the project. How do I do this?

If you are using qmake, the standard Qt build system, just add a line to the .pro file as documented in the qmake Variable Reference:

INCLUDEPATH += <your path>

If you are using your own build system, you create a project by selecting "Import of Makefile-based project". This will create some files in your project directory including a file named <your project name>.includes. In that file, simply list the paths you want to include, one per line. Really all this does is tell Qt Creator where to look for files to index for auto completion. Your own build system will have to handle the include paths in its own way.

As explained in the Qt Creator Manual, <your path> must be an absolute path, but you can avoid OS-, host- or user-specific entries in your .pro file by using $$PWD which refers to the folder that contains your .pro file, e.g.

INCLUDEPATH += $$PWD/code/include

For anyone completely new to Qt Creator like me, you can modify your project's .pro file from within Qt Creator:

Just double-click on "your project name".pro in the Projects window and add the include path at the bottom of the .pro file like I've done.

To add global include path use custom command for qmake in Projects/Build/Build Steps section in "Additional arguments" like this: "QT+=your_qt_modules" "DEFINES+=your_defines"

I think that you can use any command from *.pro files in that way.

If you use custom Makefiles, you can double click on the .includes file and add it there.