Simple and functional extension. It checks the container of each tab, so there's no risk of closing tabs with the same URL, but with different credentials (be careful, though, that if a site manages states using cookies, local storage or anything else that doesn't change the URL, the extension will consider the tabs as duplicates and close them.) It pops a message telling how many tabs were closed.

very very g0od addone. i cant live without it. works in all Firefox new or old edition. also supported in waterfox classic edition which is based on old firefox engine

It is a very simple and useful extension.

I did something stupid and created 160 bad tabs in a few seconds. After installing this addon, my mess was cleaned up instantly.

I like having dozens of tabs open, but it drove me nuts having duplicates. I wanted a very simple solution to clean them up. Now a few times a day I click on the icon and, "wallah!".

It tells me how many closed. I feel somehow less overwhelmed - and go back to work. Thank you :)

That's it.

Doesn't work at all on Firefox for Android.

It's a usefu tool. I liked so much.