Recs.
Updated
Saves up to 95% of memory because it reduces the number of open tabs in Google Chrome and Mozilla Firefox.
Specs
Pros
Pro Overall very useful
It takes all of your tabs (choose between all/all-except-current/current/all-to-right/all-to-left) and turns them into links in a special OneTab tab where you can further manage your tabs by dividing them into groups, removing duplicates and securing them so that they can't be removed unless unsecured.
Pro Non-invasive
The OneTab dashboard only appears the first time you open your browser after quitting, although you can also make it appear through the extension button in the extensions bar. This is less invasive behavior than the Chrome extensions that appear every time you open a new browser tab.
Pro Provides just enough information
OneTab provides just the right amount of meta-info about the tabs you've saved. It groups them by session, and tells you how many tabs are in each session, as well as the date the session was created. Every saved tab includes the bookmarked favicon and page title.
Cons
Con Slightly confusing UX
It's easy to forget that clicking on the OneTab button in the extensions bar doesn't show you options – it saves your current session by closing all your tabs in the given browser window. That might be slightly annoying if you were trying to access the OneTab dashboard or view OneTab options instead of trying to save your current session in OneTab, but this is only a minor inconvenience given how easy it is to restore your session.
Con Clicking on a tab/link to re-open it automatically deletes it from a session
This is not so much a con as much as it is a heads up for those who use OneTab as a form of transient digital bookmarking (like me!). When you click on a tab/link in any given OneTab session, that will cause it to disappear from the list of tabs in that section. It would be nice if there was an interim period or separate place where the link is still visible/accessible. That or it would be nice to have a version history of past closed tabs/links and sessions.