Capturing video with internal audio using QuickTime Player in Mac

QuickTime Player in Mac has the provision to record screen. However it does not capture system audio since only the audio from the microphone is captured.

Sound Flower helps in capturing the System audio along with the video:

Step 1:
Install Sound Flower from the link below:
https://code.google.com/archive/p/soundflower/downloads

Step2:
Go to Settings --> Sound. Change the settings as below:




Step 3:
Go to Quick Time player and select New Screen Recording. Make sure the selection is proper:

Select the portion you want to record and hit "Start Recording".

Note that you won't be able to hear system audio while using Soundflower as a QT input--the audio that was going to your speakers is now going into QT instead. When you finish your recording, go back to System Preferences > Sound > Output to route the audio back to Internal Speakers or your usual default audio output.