To try the thousands of add-ons available here, download Mozilla Firefox, a fast, free way to surf the Web!
CloseWelcome to Firefox Add-ons.
Choose from thousands of extra features and styles to make Firefox your own.
CloseReview for Duplicate Tab by Jack
Rated 5 out of 5 stars
I've been happily relying on this simple little workhorse since it was first brought to my attention that such a basic feature was missing from firefox. It does exactly what it says, with no excess baggage.
FF terminated it with prejudice, though, so https://addons.mozilla.org/en-US/firefox/addon/duplicate-in-tab-context-menu/?src=userprofile seems like a decent replacement.
To create your own collections, you must have a Mozilla Add-ons account.