In the nightly builds of Firefox, on which the release of Firefox 129 will be based on August 6, a new implementation of the sidebar and the ability to arrange tabs vertically have been added. This allows for additional screen space to view website content on widescreen displays (since April, vertical tabs have been tested in separate larch builds, and are now available in standard nightly builds). To enable vertical tabs, you need to activate the sidebar.revamp and sidebar.verticalTabs options on the about:config page. The sidebar can be displayed in both expanded and minimized views. In the expanded view, part of the page titles in the tabs and the names of operations moved to the sidebar are shown, while only the icons of sites and operations are visible in the minimized view.
Source: opennet.ru
