CtrlCmdU

CtrlCmdU is a keyboard shortcut that combines the Control key, the Command key, and the U key. It is used in some cross-platform software to invoke a text formatting command on the current selection or insertion point.

In many applications, the U key is associated with underline. Across platforms this is commonly mapped as Ctrl+U on Windows and Linux, and Cmd+U on macOS. CtrlCmdU is an approach used by developers to provide a single, platform-neutral mnemonic for the underline action. When supported, pressing CtrlCmdU toggles underline formatting for the selected text or applies underline to new text.

Support for CtrlCmdU varies by application and version. Some programs implement it as the universal underline toggle, while others may reserve the U key for different actions or rely on platform conventions. The shortcut typically requires focus in a text area and may behave differently in rich-text versus plain-text modes. Users with keyboard remappings may see different results.

Because it involves three keys, conflicts with other shortcuts can occur, and users can usually customize bindings in the application settings or OS-level keyboard shortcuts.

See also: Ctrl+U, Cmd+U, Underline (typography), Keyboard shortcut, Text editor.