Installed and allowed in Private Browsing but it wasn't working for me at all. The button appeared in my toolbar ok but there was no tab count, only a black box.

Hovering over the toolbar icon, I get a tooltip "Tab statistics not yet initialized" but it's been several minutes at least (even before I started writing a review) and there is no indication that it is even working on "initializing". According to my other tab counter addon, which I was hoping to replace with something bigger ('Tab Count Icon by lllusion3418') I see that I currently have 217 tabs open ... according to the screenshots for this addon, it ought to be able to handle over 1000.

I have tried clicking the toolbar icon and if it is doing anything, then it is not doing a very good job of relaying that to the user... But I suspect it is just not working.

Even if it was working, I see that there is no preferences section for this addon so it is unlikely that I would be able to custom colors (which I can do in my current addon) or increase the font size.

Best of luck, but for now, I'll keep looking or stick with what I have.

FF v89.0.2 on Fedora 33 Cinnamon