How to create a blurred UI effect?

Hey,
I wonder how it is possible to create such an OnScreen(UI) blurry effect: https://youtu.be/c1eyeXGx51s?t=86 or how to create such an air/fall OnScreen(UI) effect: https://youtu.be/C4UGAIEZm4A?list=PLop-8mIH2JNfjzbcRuKlJmSqE4v0Ar5UW&t=204

Thank you guys :slight_smile: