SequoiaView is described as 'Create a visual representation of the amount of space each file is taking on your hard drive. It creates a "squarified treemap" that makes it easy to see where all your space is going' and is a disk usage analyzer in the system & hardware category. There are more than 50 alternatives to SequoiaView for a variety of platforms, including Windows, Mac, Linux, BSD and Flathub apps. The best SequoiaView alternative is WinDirStat, which is both free and Open Source. Other great apps like SequoiaView are WizTree, Baobab Disk Usage Analyzer, TreeSize and SquirrelDisk.
Very fast and lightweight!