you can download TabSweeper here
What is TabSweeper
I can't stand it when I've got more tabs open than I can see. Firefox (and basically all browsers for that matter) just doesn't have a useful way to manage tabs that is also compatible with its new multiprocess architecture. I used to use one-tab, but it's a legacy add-on and as far as I can see it will cease to work this November with the release of Firefox 57.
I took a look at the documentation for Firefox's web extension APIs and figured I'd give writing my first extension a try. This extension would re-implement the core functionality of one-tab - which closes all your open tabs and stored the URLs for later viewing, where you can either restore them or delete them from memory.
One-tab uses a special tab interface to manage your saved sessions, but I decided to use Firefox's new sidebar feature instead. It's easy to toggle visibility in and off, and you can still see what you've got open in your active tab. The sidebar can be toggled using a keyboard shortcut or through the sidebar button on the browser toolbar. The tab cleaning function is also bound to a keyboard shortcut, making cleaning tabs up really easy.
The sidebar is very basic at the moment, but it's functional. I plan to optimize the interface and how it's updated. I also plan on removing bootstrap and using some custom CSS, since bootstrap was only used for MVP purposes.
If you're interested in trying out TabSweeper, the signed add-on can be downloaded from the GitHub releases page. I hope to get it up on the Mozilla add-ons site, but that's blocked for now while the add-on awaits a code and security review.
If you have any feedback, suggestions, or bugs to report, file an issue in GitHub or send me an email