SpaceSharp
Open-source Windows disk space analyzer with interactive treemaps
...Features include fast parallel scanning, multiple treemap styles, search and filtering by name, extension, file type, size and age, largest files and folders views, storage breakdown by file type, actual size-on-disk measurement, hard-link detection, file-type coloring, multiple color palettes, dark and light themes, and Windows theme support.
Files can be opened in Explorer or safely removed through the Windows Recycle Bin. SpaceSharp is available as both portable and installable builds.
The project is released under the MIT License and is actively developed on GitHub.