Excellent.

Drawback: the add-on seems to have been abandoned 4 years ago, as seen on Github:
https://github.com/Peuj/duplicate-tabs-closer

But I find a bug:
Whatever your choice in "Priority" parameter in the Options, the add-on always keeps the oldest visited tab. This parameter seems to not work at all.

And I also have two little requests:
- First one: it would be nice not to include the tabs "New tab" in the list.
- And second one: it would be nice to disregard (ignore) a final "/".

Both requests could have their checkbox in the Option page (with On by default).

But I don't know what to think, given that the developments seem to have been abandoned 4 years ago.

Seems to work fine BUT ONLY IN ONE WINDOW ... I uses several windows and there are "no duplicates" found by this (and other) tab deduplication extension ...

Because of some somehow gone/lossed tabs I opened a saved session so I had to get rid of duplicated tabs.

Works well - the option to delete newer duplicate tabs goes a long way to not losing anything you're looking at or working on.
Would be cool if there could be a colour, or some kind of alert or badge on the actual dupliacte tab itself.
A one-click, auto-appearing 'close' button would be good too, instead of having to dive into the menu.

I find the 'close all' button and section a bit unclear - both the duplicate and the original tabs are listed, with a cross by each. Does the cross close the tab, or remove it from the menu? Does the 'close all' button close all the listed tabs, or just the duplicates? It's a bit nerve-wracking at first, but once you get used to how it works it's helpful in pruning down serious browsing sessions.

Excellent add on! Can we please get an option to exclude duplicates when a duplicate tab is manually opened?

I tried a duplicate tabs extension that was way simpler than this that I liked at first. It could close duplicate tabs automatically in the background without interruptions, but it stopped working at some point. I tried this one next and it seems to be very robust. I wasn't sure that I needed all the bells and whistles at first but they have turned out to be quite useful after all, such as the URL format filters and the whitelist.

If I could add a suggestion, it would be super helpful to be able to whitelist a new tab. Not sure if this is possible. I tried entering a pair of empty double quotes into the whitelist field "" to see if that would work since I noticed that wildcards are also supported. Kind of a hackerly solution but I took a swing at it. Still closes them though. 😛

Recently the about:blank whitelist fails.

This Extension is nearly perfect! The best of the duplicate tab closing extensions on Firefox. I would love to see a couple features that I think would push this into the perfect 5* range.

[1] Whitelist should be available with the 'do nothing' option so that it applies to the "Close All" button as well, so that I can exclude certain pages (such as New Tab or about:blank) but still use that option.
[2] Add the option to pop up a Notification on duplicate. Automatically removing tabs has caused me issues, so I do not use that feature, but I still would love an option to know when I am duplicating an existing tab in the moment.
[3] In the duplicate tab notification window it would be nice to have the options to close New or Old duplicated tab, or to do nothing.

Thanks for all the hard work!

-Shrunk mode bug-
when all options are unpinned and then all options are hidden by shrunk mode, I can't unhide them again. when I click shrunk mode button, nothing is happens.

The problem is that there are cases when all duplicate tabs are closed without keeping neither of them or both
-auto-close on
-no filters
-keep newer tab (keep tab with HTTPS, keep pinned tab)
-scope: active window

The situation occurs when both tabs were loading simultaneous!

This is really handy and has a good set of options for fitting into whatever way you like to browse. You should absolutely give this a try, and open the options panel if it doesn't suit you out-of-the-box.

The one extra thing I'd like to see is an option to have settings like "ignore path" apply to particular domains only -- I'd love to be able to open four articles from the same website but reliably collapse four instances of the same web-app.

Super extension overall, but there is a bug in the settings handling for filters.
If "Ignore search part..." is set, then "Ignore hash part ..." isn't doing anything. Similarly of "Ignore path part ..." is set then the two other settings are useless.

This is due to "else if" being used in areMatchingURL function from urlUtils.js (line 24, 28). Switching this to independent ifs allows to respect all settings (and support urls having both hash and search signs.

If possible please bring a fix for this one (I can provide a pull request if the code is on some git repo).
Thanks in advance.

since Fire Quantum, no longer shows mini-window indicating duplicate tabs.

Shows the wrong number of duplicates.
More than really, even if real quantity of duplicates = 0
Perhaps it's conflict with "Tree Style Tab" or "BarTab Plus".
my FF version - 55.0.3 (x64)

UPD

https://addons.mozilla.org/firefox/addon/tree-style-tab/versions/?page=1#version-0.19.2017090601

https://addons.mozilla.org/firefox/addon/bartab-plus/

OK. I found how the conflict appears - when I use the "Unload" option of "BarTab Plus". "Duplicate Tabs Closer" defines the unloaded tabs as duplicates for some reason.