Your Synology already ships with a duplicate finder. So why would you need anything else? Because of the small print. Storage Analyzer is genuinely useful for an overview, but its own spec sheet lists limits that bite exactly when your NAS is full enough to need help.
What Storage Analyzer can't do (from Synology's own spec)
Synology documents four hard limits on Storage Analyzer. Each report stops at 5,000 duplicate files. Only the 200 largest files appear in the large-files section. If you have more than ten volumes, only the 10 most-used are shown. And Hybrid Share folders are excluded entirely.
The first one is the real problem. A family NAS that has collected phone backups, photo imports and copies of copies for a few years routinely holds tens of thousands of duplicates. A 5,000-line report doesn't just truncate the list, it hides how much space you could actually reclaim.
See every duplicate, not the first 5,000
NAS Ranger has no report cap. It scans your Synology shares in full and shows every duplicate group, with the exact gigabytes you'd get back. It finds them by content, not by name (size first, then a cryptographic fingerprint only when sizes match), so two files with different names but identical bytes are still caught, and two files that merely share a name are not falsely flagged. If you want the detail of how that works, see how to find duplicate files.
Clean up in bulk, without fear
Finding duplicates is half the job. Storage Analyzer reports them; you still have to go remove them by hand. NAS Ranger lets you act on hundreds at once from a clear interface, and it never deletes in place. Confirmed duplicates are moved to a trash folder on the NAS, a rename that's instant even for large videos, so you review before you purge. Here's why that stays safe.
Nothing to install on DSM, and it survives updates
Storage Analyzer lives inside DSM, so it changes when DSM changes. NAS Ranger runs on your computer and speaks SMB natively: it connects straight to your Synology shares, with nothing added on the NAS side. There's no package to add, and a firmware update can't take the tool away from you. The same app also works on Windows, macOS and Linux, and on any other NAS you own.
Try it free: scan your Synology, see every duplicate and the exact space you can reclaim, well past 5,000, before you touch a single file.