After SOOO much searching, SUPER Happy to found this.

I am using this in Zen Browser, I want new tabs to open at the top of side bat (Technicaly at far left on Firefox) , LOVE it Thanks 👍

Now don't need to switch to new tab that at the end of border every time.

Now I know where to look for my new tab without other tabs confusing me.

Lacks the most important option: Move tabs to the bottom.

*UPDATE
Dev fixed the issue with settings not saving that was super annoying. It works great now!

Custom settings get reset to defaults on every browser restart. Have to manually restore saved settings. Every single time.

Najlepszy!

Thanks for sharing this extension as everyone else seems obsessed with the Open Right behavior. I like the options but unfortunately it does not work with the current version of Firefox. I'd love to try this again when it's working.

Very interesting. Thanks Kunihiro !

Very nice add-on! Congrats Kunihiro!

Please, I have three simple requests:

1) Please add an option to open tabs always in "unloaded/inactivate" state. With this option, new tabs always will load/be activated only when selected. This is great for browser performance, saving RAM/CPU etc.

2) Please, add an option for opening all links in new tabs. Current function only opens external links in new tabs. It'll be great to have the option to open 100% of the links (internal & external), always in new tabs.

3) Some functions at "options"... I have no idea what they are for ("Loading Page"?). It will be nice to add some explanations at your AMO' page.

Thank you!

Excellent, make almost EVERY TAB (include newtab from urlbar/searchbar and newtab button)be opened in Background.
But it's only valid when its option page opened.

Great Addon!
But it seems like working well in Chrome, But not in Firefox, hope to fix this problem.

Excellent add-on! Thank you, Ando! I also use your add-on Google Chrome and I'm very pleased with that.

Works good. But there is no option to disable shortcuts for tab reorder.
This shortcuts made me angry after unintentional pressing.

Excelent, please Firefox for Android version. thanks

Thank you Developer! Something that actually works & functions as described. I've uninstalled several addons that claims to do this. This one actually works!

Finally! I loved this on Chrome, so I'm glad it's on Firefox too.

It's working well.The option remains saved after closing the firefox and start again.

This extension works as advertised, after removing other extensions that affect tab opening/closing behavior. The only issue I've found is that it doesn't save any adjusted settings after restarting a new session, and instead reverts to the browser's defaults.