Open Tab Right, Close Tab Left by T444W

Open Tab Right, Close Tab Left gives you predictable, intuitive tab behavior in Firefox.

Opening tabs: Every new tab opens immediately to the right of your current tab — never at the far end of the tab bar. This works for Ctrl+T, Ctrl+click, middle-click, right-click → Open in New Tab, target="_blank" links, bookmarks opened in new tabs, and duplicated tabs.

Closing tabs: When you close a tab, focus always moves to the tab immediately to its left. No more jumping back to a random "source" tab across the bar.

Tab group aware: If you're working inside a tab group, close behavior stays within your group — focusing the left neighbor inside the group first, only leaving the group if it's empty. New tabs opened from within a group stay in that group, even from the last tab.

Two simple toggles in the popup let you enable or disable each feature independently.