Control-Y is a common computer command. It is generated by holding Ctrl and pressing the Y key on most computer keyboards.
In most Windows applications this keyboard shortcut functions as Redo, reversing a previous Undo. In some programs such as Microsoft Office it repeats the previous action if it was something other than Undo.[1]
Apple Macintosh systems use ⌘ Command+⇧ Shift+Z for Redo.[2] In general a shortcut on Macintosh using ⌘ Command matches up with a shortcut on Windows using Ctrl, this is one of the most noticeable conflicts. Many programs (on all systems including Linux) support both Ctrl+Y and Ctrl+⇧ Shift+Z for Redo to resolve this conflict. But quite a few remain where only one or the other shortcut works.