This extension implements a concept similar to Pinned Tabs, but for Firefox
windows. Once a window is pinned, all new tabs that would have previously
been opened in that window are now opened in a different, non-pinned window.
It is most useful for people who generally have multiple Firefox windows open,
with each window dedicated to a particular site or task.
Note that you can still drag and drop tabs to and from pinned windows - this
only affects new tabs that would be opened by clicking on a link.
This extension adds a new item to the Context Menu (or for Firefox 53 and earlier, the Tools menu) - "Pin Window" which toggles the pinned state for that window. The pinned
state is stored with SessionRestore, so the pinned or unpinned state of
windows remains across browser restarts.
You use IRCCloud for IRC conversations, and have IRCCloud open in its own window. Normally, if you click on links in the IRC channel, links are opened in the same window with IRCCloud open.
If you pin the IRCClould window, such links now open in a different browser window.
You have a window open which is dedicated to listening to music - eg, this window might have a Pandora tab open along with a streaming radio station.
If you interact with this window (eg, start music playing), then go back to reading your email via Thunderbird, then click on a link in your email. Normally, this link will open in this music window, as that is now the most recent Firefox window you interacted with. You then need to drag the tab back to a normal window so the music window keeps only music related sites open.
If you pin this music window, the link you follow from your mail client will open in a different browser window instead of in the music window.
See https://github.com/mhammond/firefox-pinned-windows for more