TreeSize

TreeSize is a disk-space analyzer from JAM Software GmbH in Trier, Germany, and has been used by millions worldwide for over 25 years.

It scans a drive once and shows what is filling it in a treemap, pie chart or sortable list, so the folder eating 40GB stops hiding three levels down. Duplicate detection, bulk delete, move and rename, and scheduled PDF, Excel or CSV reports round it out, and the whole thing runs on-premise with no cloud dependency — nothing it scans ever leaves the machine.

There is a genuinely free edition for home, non-commercial use, alongside a Personal edition at €20.40 a year for freelancers and small businesses, and a Professional edition from €40.80 a year for IT administrators who need to run it across a whole server estate. Both paid tiers carry a 14-day trial. JAM Software GmbH's own imprint names a Handelsregister entry in Trier (HRB 4920) and a German VAT ID, rather than a support address behind an anonymous brand.

TreeSize does one job and does not try to be a suite. It will not clean the registry, manage startup programs or tune Windows privacy settings the way Ashampoo WinOptimizer or O&O ShutUp10++ do; what it does is tell you, precisely and quickly, where your disk space actually went, which is the step every other cleanup tool in this category skips past on its way to a single "optimize" button.

What TreeSize does well

• Genuinely free edition for home use
• Treemap view finds space hogs in seconds
• Duplicate finder and scheduled reports built in
• On-premise, no cloud dependency
• German company with a published Handelsregister entry

Where TreeSize falls short

• Windows only
• Personal and Professional editions are yearly subscriptions
• No cleanup automation beyond what you choose to delete
• No macOS version

Standout feature. A treemap that finds the actual space hog in seconds, from a German company that has shipped it for 25 years.