DiskGeek

DiskGeek scans any folder or drive and shows exactly where the disk space went.

A sortable list view is the fastest way to see what is biggest. A squarified treemap makes the largest consumers obvious at a glance. Duplicate detection works byte for byte and, for images, by perceptual hash, so near-identical photographs are found as well as exact copies. Snapshots let two scans be compared over time.