ncdu, TreeSize, WinDirStat, DaisyDisk, WizTree, Baobab Disk Usage Analyzer, FreeCommander, GrandPerspective, SpaceMonger, WhatSize, OmniDiskSweeper, Folder Size Explorer, SequoiaView, DiskUsage, crossdirstat, Diskitude, Grid Size File Manager, DiskSavvy, Disko, JDiskReport, Filelight, Xinorbis, DiskView, Large Files Finder, Spacie, HDGraph, QDirStat, FSV, FolderSizes, Disk Space Fan, Directory Report, xdiskusage, DiskWave, Space Radar, FatFileFinder, Disk Xray, Disk Usage Reports, FilePro, TreePie, Total Directory Report, K4DirStat, RidNacs, i.Disk, 1Tree Pro, SpaceObServer, GetFolderSize, DiskMapper, PA Storage Monitor, Disk Space Fan Pro, Precious Disk, ClearDisk, xdu, Disk Space Pro, DiskTriage, GD Map, Disk Space Finder, Purple Tree, FTPpie, UtilStudio Disk Space Finder, Diskvision are some alternatives to SquirrelDisk.