You can view a scaled-down version of your program while browsing in the XFINITY X1 guide. Here's how.
Watch a Program While Browsing in the Guide
On the remote, press the Guide button once to access the main guide.
Press the square B button on the remote to open a scaled-down version of the program window in the right-hand corner of your TV.
Browse through the guide as normal. Your program will continue to play in the corner of the TV.
To dismiss the program window, press the B button again.
Alternately, to lighten the guide so you can view the program in full screen while the guide displays, you can change the Background Darkness Level in Settings. See X1: Managing the Background Darkness Level for detailed instructions.
You can also use the B button to access the program window while in any of the menu options accessed from the xfinity button: Saved, On Demand, Search, Apps, and Settings.