Alternatively referred to as Control U and C-u, Ctrl+U is a shortcut key most often used to underline text.
How to use the Ctrl+U shortcut key
On Apple computer keyboards, the Ctrl key is labeled as "control."
Ctrl+U in an Internet browser
In Internet Explorer, Ctrl+U opens the Debugger.
Ctrl+U in Excel and other spreadsheet programs
In Microsoft Excel and other spreadsheet programs, pressing Ctrl+U when one or more cells is selected will underline or remove the underline on the selected cells. If editing the contents of a cell with no selected text, Ctrl+U turns on and off underline for all contents of the cell.
If you're editing the contents of a cell and press Ctrl+U, nothing will happen.
Ctrl+U in Microsoft PowerPoint
In Microsoft PowerPoint, the Ctrl+U shortcut key underlines any selected text.
Ctrl+U in Outlook
In Microsoft Outlook, pressing Ctrl+U marks a selected read e-mail as un-read.
Use the shortcut Ctrl+Q to mark a selected e-mail as read.
Ctrl+U in Word and other word processors
In Microsoft Word and other word processor programs, highlighting text and pressing Ctrl+U adds an underline below the text. If the text is already underlined, highlighting the text and pressing Ctrl+U removes the underline.