Vertical tabs, an address bar and a new settings page.

New
- Vertical tabs in the style of Firefox and Zen. The classic horizontal tab strip is still available and can be chosen in the settings.
- Essentials, Pinned and regular tabs. Right-click a tab to pin it or add it to Essentials. Essentials are outlined in the color of their favicon. Pinned and Essential tabs have no close button, so they cannot be closed by accident.
- An address bar with back, forward and reload, a copy-link button, an address field, and a history button that lists the pages you visited in that tab. It sits across the top with vertical tabs and below the tab strip with horizontal tabs, and it can be turned off.
- Compact mode shrinks the tab bar to a thin strip of icons. It can expand when hovered, floating over the page or pushing it aside.
- Auto-hide hides the tab bar, the address bar, or both until you hover their edge.
- A settings page (about:addons, or the gear at the bottom of the tab bar) for layout, tab bar side, compact mode, auto-hide, hover style, tab display, three tab sizes, the Essentials background box and which toolbar buttons to show.

Improved
- The close button now appears only when you hover a tab, and it no longer pushes the tab's name aside.
- Back and forward only appear when there is a page to go back or forward to.
- Reload no longer adds an extra entry to the page's history.
- Existing tabs and the display-mode setting carry over automatically.

Notes
- No new permissions. Your tabs, settings and each tab's recently visited pages (address and title, up to 30 per tab) stay on your device. Nothing is collected or sent anywhere.
- Firefox decides which side of the window the sidebar is on. "Tab bar side" moves the tabs inside the panel.