Copy PlainText is a tiny extension that removes the formatting from the selection before copying/pasting to/from the Clipboard. Note: None of my extensions contain any tracking, advertising or privacy infringement. Features

Removes the formatting from the selection before saving to the Clipboard (Firefox restricts some functions on some URLs.)
Custom Find & Replace (string & Regular Expression) (v1.13)
Removes the spaces from the start and end of the selection
Removes multiple spaces
Keyboard Shortcuts: F7
Custom Keyboard Shortcut
Paste PlainText
Option to remove line indents
Help Guide included in Options page

Apple/Mac Users: if the shortcut keys do not work, try System Preferences - Keyboard - then check “Use all F1,F2, etc. keys as standard function keys." Note: WebExtension API does not allow setting Copy PlainText as the default copy function of the browser at the moment. Permissions Explanation:

Get data from the clipboard: Used to Paste Clipboard text
Input data to the clipboard: Used to Copy to Clipboard
Download files and read and modify the browser’s download history: Used by the user to export preferences to the computer (nothing to do with download history)
Display notifications to you: Used to inform users

Developer response