Choose a screen size
You can set a movie to play at the size that best fits how you want to watch it.
After you open the movie, choose a size option from the View menu:
Enter Full Screen: The movie is displayed as large as possible and the menu bars are not visible. To exit full-screen view, press Escape.
You can also click the Full Screen button in the upper-left corner to enter full-screen view. To leave full-screen view, move the pointer to the upper-left corner of the screen, then click the Exit Full Screen button . For more information, see Use apps