Which fits your needs?
JDiskReport: Users who want cross-platform disk statistics and already use Java.
NullDisk: Mac users managing local/remote storage, and developers who need Git-aware cleanup or scriptable disk reports.
Features, pricing, and workflow
Scroll across to compare
| Feature | JDiskReport | NullDisk |
|---|---|---|
| Best fit | Users who want cross-platform disk statistics and already use Java. | Mac users managing local/remote storage, and developers who need Git-aware cleanup or scriptable disk reports. |
| Visualization | Overview statistics charts and detail tables | Radial map, treemap, and file list; CLI terminal treemap |
| Platforms and requirements | macOS, Windows, Linux (Java) | Mac app: macOS 14+; CLI: macOS, Linux, Windows |
| Pricing and editions | No-charge, ad-free freeware; this does not mean open source. | Direct Mac edition free with reminders; optional $9.99 one-time personal license or team seat removes reminders. App Store terms are separate. |
| Open source | No | No |
| Native macOS UI | Cross-platform interface | Yes |
| Cleanup workflow | Use the statistics to guide file review; the cited overview does not specify removal semantics. | Review source and action: local Trash, explicit permanent removal, or backup/delete; remote and cloud actions depend on the destination. |
| Reports and portability | Preserve any saved scan files supported by your version and keep important table entries. NullDisk does not import JDiskReport scan files. | CLI produces JSON/NDJSON scan reports. Third-party scan files are not directly imported into the Mac GUI. |
JDiskReport: what stands out
A good fit for users who want cross-platform disk statistics and already use Java.
JDiskReport: strengths
- Disk usage statistics in charts and tables
- Runs across Java-capable desktop systems
- Free without ads or expiry
Considerations
- Requires a compatible Java runtime
- Freeware rather than an open-source project
- Check the manual for report storage and file-management actions
NullDisk: what stands out
A good fit for Mac users managing local/remote storage, and developers who need Git-aware cleanup or scriptable disk reports.
NullDisk: strengths
- Radial and treemap views with local, SSH, and cloud sources
- Git-aware development cleanup for generated output and eligible worktrees
- Native Mac UI plus terminal UI and JSON/NDJSON CLI reports
Considerations
- Desktop GUI requires macOS 14+; Linux/Windows use the separate CLI
- Mac app sends anonymous usage telemetry; no in-app opt-out at this review
- No content-based duplicate finder; allocated bytes are not a guaranteed recovery total
For a useful comparison on your own drive, match the scan root, access permissions, and size mode. Chart style changes how you explore the results; it does not by itself establish measurement accuracy.
Common questions
When should I choose JDiskReport?
A good fit for users who want cross-platform disk statistics and already use Java. No-charge, ad-free freeware; this does not mean open source.
When should I choose NullDisk?
A good fit for Mac users managing local/remote storage, and developers who need Git-aware cleanup or scriptable disk reports. Direct Mac edition free with reminders; optional $9.99 one-time personal license or team seat removes reminders. App Store terms are separate.
Will both apps show the same size?
Not necessarily. Match the scan root, permissions, exclusions, and logical/allocated-size mode. Hard links, APFS clones, snapshots, sparse files, and cloud placeholders can change totals. A reported size is not a guaranteed amount recovered after deletion.