ctrl+shift+v, middle-click and ctrl+v all gives me different results when pasting into URxvt, code, or Firefox. Can't seem to find a way to unify the clipboards. Even the Arch wiki doesn't explicitly tell you how. Please assist.

Edit: ‘Unifying’ the clipboards was the wrong term. I just want to be able to paste text from the clipboard buffer onto URxvt (a terminal that only accepts the primary buffer).