Vivaldi
Vivaldi is a free, highly customizable web browser released on April 6, 2016. It is developed by Vivaldi Technologies, a company co-founded by Jon Stephenson, a co-founder and former CEO of Opera Software. He launched Vivaldi in response to community displeasure with the Opera web browser. With Vivaldi, he wanted to create a browser that recaptures the minimalism and customizability of the original Opera.
Features
The Vivaldi browser UI (user interface) is designed to "get out of the way." It features unobtrusive buttons and menus, and an optional "Chromeless UI" for maximizing screen real estate. Like the original Opera, the Vivaldi background color can change to adapt to the color scheme of the current website. The browser also offers mouse gestures, enabling the user to control the browser by moving the mouse in certain ways.
Technology
Vivaldi is based on Chromium, the open-source version of the Chrome web browser. Its UI is implemented as a React application, which uses HTML5, CSS (cascading style sheets), and JavaScript to create the browser's front end. Because it's based on Chromium, many extensions designed for Chrome can be installed in Vivaldi directly from the Chrome Web Store.
The source code of Vivaldi is available for anyone to view or audit for security purposes.