App to learn to sing in key

Hi Everyone, just wanted to check if there is any app to check if we are singing in key? As a beginner , I have a hard time matching pitches/keys and looking for resources to practice on that. 

Check out SingTrue, SingScope, Yousician, Nail the Pitch, SingSharp, and more in this thread: https://www.reddit.com/r/singing/comments/13gfe0c/websitestools_to_help_with_pitch/?rdt=37083. 

Lots of options, each with pros and cons! 

This lesson series as well if you haven't already:

https://www.30daysinger.com/tutorial/how-to-sing-in-tune-for-beginners-part-1