Firefox Quantum (Firefox 65) uses tabs on top
How to place tabs on bottom
This article shows you how to change Firefox’s appearance from tabs on top (where the tabs appear above the URL address bar) to display the tabs below the URL address bar.
Before the release of Firefox Quantum (i.e. FF v57), it was possible to change the location of the tabs by changing a browser parameter setting. The setting was
FF still retains the parameter but its functionality has been disabled; browser tabs remain on top (above the URL address bar) regardless of this parameter’s value. We will see how it’s possible to change the location of the tabs.My earlier article, Firefox: tabs on bottom, discusses an older version of FF. This article updates that advice following the release of FF65.