Vivaldi is described as 'is extremely customizable, presenting a wide range of settings and built-in features designed to put the user in control' and is a leading Web Browser in the Web Browsers category. There are more than 100 alternatives to Vivaldi for a variety of platforms, including Windows, Mac, Linux, Android and iPhone. The best alternative is Mozilla Firefox, which is both free and Open Source. Other great apps like Vivaldi are Brave (Free, Open Source), Google Chrome (Free), Tor Browser (Free, Open Source) and Opera (Free).
Sidekick is a revolutionary new work OS based on the Chromium browser. Designed to be the ultimate online work experience, it brings together your team and every web tool you use – all in one interface.
Abrowser is Trisquel's version of Mozilla's popular web browser with the trademarked logos replaced. Replacing the trademarked logos gets rid of the trademark restriction that forbids selling the software, which would have effectively made it non-free software.
Whale is web browser developed by Naver Corporation.
Whale possess a lot of similar features as Vivaldi as being a customized pushed browser, multi-tasking browsing called 'Omnitasking', as much as other features as cloud saves & quick translation.