GNU Emacs

12.3 “Cut and Paste” Operations on Graphical Displays

In most graphical desktop environments, you can transfer data (usually text) between different applications using a system facility called the clipboard. On X, two other similar facilities are available: the primary selection and the secondary selection. When Emacs is run on a graphical display, its kill and yank commands integrate with these facilities, so that you can easily transfer text between Emacs and other graphical applications.

By default, Emacs uses UTF-8 as the coding system for inter-program text transfers. If you find that the pasted text is not what you expected, you can specify another coding system by typing C-x RET x or C-x RET X. You can also request a different data type by customizing x-select-request-type. See Coding Systems for Interprocess Communication.