Firefox OneTab - One tab to rule them all

Updated: September 7, 2020

Occasionally, I get sent software recommendations by email. Believe it or not, I try to test as much as I can, even though it takes me years to go through the wishlist. And sometimes, I skip the queue, because a particular application looks rather interesting. One such example is OneTab.

This is a Firefox extension, for the post-Quantum world. Indeed, I've lamented the loss of Tab Mix Plus, as it was one of the best, most versatile add-ons for the browser EVAR made Since Firefox 57, I've been a-huntin' for a nice, elegant session manager with gusto. I did find one reasonable candidate - Session Sync. Now, there's another potential champion of tabs, and it's called OneTab. Let's see what gives.

Promising, promising ...

OneTab looks deceptively simple. And it is. But then, it also packs quite a punch. This is how it works. You go about browsing. Then, when you want to group all your tabs into a list, you hit the OneTab icon. The tabs will disappear (close), and you will get them listed inside the OneTab interface. At this point, you can name the group, lock it to prevent deletion, individually remove specific sites from the list, star the list so it shows up as a favorite, and a few other tricks.



Group locked and named

Using OneTab


You can further customize how OneTab behaves. By default, it has some weird options. Every time you launch the browser, you get the OneTab to open and take focus, and this can be annoying. But you can disable this. Furthermore, OneTab will delete a group once you restore it - you can also override this. Then, by default, it will keep duplicates.


Getting better

As you keep using OneTab, you discover its flexibility and clever tricks. First, sessions will be converted to lists only when you click the icon. If you go about browsing and then close Firefox, there's no automatic last session save (it could be nice though). You can also add websites to existing lists, or select a site to be excluded from OneTab, so when you do hit the button, it won't show.

Other tricks

And so everything was great except one thing ... sync tab loading

I was impressed with OneTab, and I decided to try it in earnest - prod use. So I installed it on a different host, and one-tabbed a session with 78 tabs, including some pretty heavy websites. When I tried to restore these later on, I almost crippled my machine.

The things is, OneTab tried to restore and load these all at the same time - not on-click. What happened was a massive impact on my system resources. The CPU spiked to 100%. The memory usage went all the way, and we're talking 16 GB of physical memory, plus the browser ate into the swap, too, another solid 4 GB. It looked like an irrecoverable situation, and I was going to run out of memory. Not a single tab really fully loaded, mind.

I then tried to close the browser - this took three minutes until it finally, mercifully responded. After Firefox went away, the memory usage dropped to about 1.5 GB, but there were still a lot of pages from other processes swapped out, which is a bit of a hassle, of course.

High resource usage

So, the lesson here is - if you got massive sessions, load them slowly, tab by tab. Which is a shame, because the built-in Firefox session save function works without problems. Similarly, Session Sync has no issues, because it uses the same on-click trick. This would be a simple configuration change to allow OneTab to handle massive multi-tab sessions.


OneTab is an interesting extension. It's got lots of goodies, plus one or two big baddies. The two immediate improvements would be not to collapse an existing session, merely create a list, and then just open on-click placeholders for tabs when restoring. This would significantly improve usability with large tab sets, because in the current guise, OneTab is only useful for small tab collections.

Other than that, this is a clever little Firefox add-on. I like the fact you can create easily accessible lists without any convoluted tricks. This is superior behavior to how Firefox does bookmarks now, and comes really close to what the old session managers of yore did. The ability to exclude sites, or merge lists, is also very neat. A simple product, with lots of hidden gems, but sometimes, the simplicity gets in the way. However, it won't take much to polish the rough bits, and make OneTab into a proper keeper. Le fin.