FreeFileSync: when to install it, and when not to
FreeFileSync is a free, open-source tool that mirrors and syncs folders between drives, NAS and some cloud targets, with a clear preview of what will…
The short version
FreeFileSync: Compares two folders and shows you exactly what will be copied, moved or deleted before anything happens, then does it and verifies the result. The clearest free tool for mirroring to an external drive.
| Licence / price | Free · Open source |
|---|---|
| Platforms | Windows, macOS, Linux |
| Category | Backup & Sync — 5 programs |
| Official download | https://freefilesync.org/download.php ↗ |
What it is for
FreeFileSync is a free, open-source tool that mirrors and syncs folders between drives, NAS and some cloud targets, with a clear preview of what will change. For keeping a backup copy current without copying everything by hand, it is the practical default.
When to pick something else
The free version is for personal use and the interface is utilitarian; very large syncs can be slow to compare. It syncs folders you point it at, so a wrong direction setting can erase the wrong side if you ignore the preview.
How it compares in Backup & Sync
These are the alternatives we would consider for the same job. The notes are the same ones used on the main list, so there is no separate ranking hiding on this page.
| Program | Licence / price | Platforms | Why it is on the list |
|---|---|---|---|
| Syncthing Publisher's site ↗ | Free · Open source | Windows, macOS, Linux, Android | Keeps folders identical across your own devices, peer to peer, with no cloud in the middle and no account. Because deletions propagate, it is synchronisation rather than backup. Pair it with versioning turned on. |
| Duplicati Publisher's site ↗ | Free · Open source | Windows, macOS, Linux | Scheduled encrypted incremental backups to a local drive, a NAS or cloud storage, with a browser interface and retention rules. Good for a home setup. Test a restore before you trust it with anything. |
| Restic Publisher's site ↗ | Free · Open source | Windows, macOS, Linux | A single command line binary that does fast, encrypted, deduplicated snapshots to almost any storage backend. The choice for people who want backups they can script and verify rather than click through. |
| Backblaze Personal Backup Publisher's site ↗ | Paid · From $99/year | Windows, macOS | Unlimited cloud backup of one computer for a flat annual fee, including external drives. The one paid subscription on this page that most households should genuinely consider, because off-site is the part people skip. Free 15-minute restore window for the first 30 days. |
Practical notes
- Always read the preview before confirming a sync.
- Use the mirror mode for backups, two-way only when both sides should change.
- Save job configurations for the folders you sync often.
Questions people ask
Is FreeFileSync open source?
Yes, GPL; a donor edition adds a few extras.
Can it back up to a NAS?
Yes, over SMB or FTP, which makes it a solid backup step.
Will it delete files?
Only according to the sync variant you pick; the preview shows exactly what.
Where it appears in our guides
See the full Backup & Sync explainer for the other 4 programs in this category.
How to read this page. How to read this page. Platform, licence and publisher details come from our directory data. Where an independent review, audit or survey is mentioned, it is summarised in our own words with the source named and linked; our /sources page sets out that policy. The recommendation, the trade-offs and every 'skip it if' line are our editorial judgement. We do not run benchmarks, publish measured performance figures or host installers, and every download link goes to the publisher's own site. If a detail is out of date, our About page explains how to tell us.