Vivaldi is a Chromium-based web browser for power users that is fast, rich in functionality, flexible and puts the user first. Vivaldi's interface is very customizable. Vivaldi combines simplicity and fashion to create a basic, highly customizable interface that provides everything a internet user could need. The browser allows users to customize the appearance of UI elements such as background color, overall theme, address bar and tab positioning, and start pages. Vivaldi features the ability to "stack" and "tile" tabs, annotate web pages, add notes to bookmarks and much more.
Thanks to nanana1 for the update.