Works for me. Just had to restart the browser and refresh the opened tabs.

Not working at this moment on last version.

I only encountered an error when managing the tabs with
Move Tab Left Ctrl + Shift + Page Up
Move Tab Right Ctrl + Shift + Page Down
The numbering was lost and never retrieved again.

Really awesome.
It will clutter your history since it prepends the tab number.
And for some reason works with "Alt" key in Linux instead of "Ctrl".

nice plug, suggest to edit font size number

It just numbers the tabs.
It doesn't get in the way.
What else could you want?

Decent addon. Would be useful to see some improvements like adding numbers only if you have more that 2 or 3 tabs, adding a '9' on the last tab..

Exactly what I wanted, done in an unobtrusive way.