"Are you used to being able to highlight text and have it instantly copied to the clipboard? Why not have this functionality in your browser as well?" -- spyrosoft This is a fork of https://addons.mozilla.org/en-US/firefox/addon/copy-on-select by late spyrosoft. See the version history on the add-on homepage for information on what has changed since the fork. Here are some cases where it is difficult or outright impossible for this add-on to copy-on-select: Technically impossible:

Firefox user interface elements outside of the main web page (URL bar, dialogues, etc.)
Special Firefox pages (about:*, view-source:*), PDF documents, XML documents
Disabled input elements of a web page

Probably possible, probably not:

JavaScript-heavy web pages, in particular if they do funny things with the selection (https://docs.google.com)
Likewise web pages that rely on JavaScript libraries like CodeMirror for text input

Please consider opening an issue on the support site or send a mail to the support email if you experience a web page where this add-on does not copy-on-select.

Respuesta del desarrollador