These two get compared constantly and they aren't the same kind of thing. Syncthing replicates folders between your devices, peer-to-peer, with no server required and no concept of a user account. Nextcloud is a server platform: files with share links and a web UI, plus calendars, contacts, and an app ecosystem. If the anxiety you're treating is "this file exists in only one place", Syncthing fixes it with a tenth of the moving parts. If other humans need links, logins, or a browser view of your files, that's Nextcloud's job. Plenty of sane setups run both.
What each actually is
Syncthing is a single Go binary per device that finds its peers (directly or via community relays), and mirrors chosen folders between them with block-level transfers, TLS on the wire, and no third party holding data. There's no "server copy" unless you decide one device is the always-on one. It idles around 30–80MB of RAM and, in my experience across roughly five years of running it, requires attention approximately never.
Nextcloud is a PHP application with a database, ideally Redis, and a sync client modelled on Dropbox: a server holds the canonical copy, clients sync against it, browsers and phones can reach everything through accounts. It's the full platform — and it costs platform prices: ~1GB of RAM to be comfortable, three major releases a year, and enough tuning surface that making Nextcloud fast is a whole article on this site.
The comparison table
| Syncthing | Nextcloud | |
|---|---|---|
| Architecture | Peer-to-peer | Client-server |
| Share a link with an outsider | No | Yes: passworded, expiring links |
| Web file browser | No (admin UI only) | Yes, full |
| Accounts and permissions | None — device IDs | Users, groups, quotas |
| iOS story | Third-party apps (Möbius Sync, Synctrain) | Official app |
| File versioning | Staggered versioning, off by default | Versions + trash, on by default |
| Idle RAM | ~30–80MB per device | ~1GB server stack |
| Maintenance | Effectively none | Regular, real |
Conflict handling, the part that actually matters
Edit the same file on two devices before they sync and something has to give. Syncthing never silently discards data: the losing version is preserved as report.sync-conflict-20260511-142530-ABCDEF.docx next to the winner. That's the good news; the bad news is nothing tells you it happened. (By default at most ten conflict copies per file are kept — maxConflicts in the folder's advanced settings tunes it.) Sweep for them periodically:
find ~/Sync -name "*.sync-conflict-*" -mtime -30Cron that weekly with a notification and Syncthing's honest-but-quiet conflict model becomes a genuinely safe one. Nextcloud's desktop client detects the same situation and prompts, or keeps both copies with a conflict marker in the name — more visible in the moment, same underlying truth. Neither merges file contents; that's what git and collaborative editors are for. If two people routinely edit the same documents, the answer isn't sync at all — it's Nextcloud's collaborative office editing, where there's one live copy.
Running both without a mess
The combination that works: Syncthing as the transport between machines you own, Nextcloud as the presentation layer for everything else. Concrete version — Syncthing mirrors ~/work between laptop, desktop, and the always-on server; the server's copy is exposed read-mostly through Nextcloud's External Storage app so it's browsable and shareable from anywhere. One rule keeps it sane: every folder has exactly one "system of record" path, and outsiders get links, not write access to synced trees. Worth knowing while placing nodes: Syncthing can hold an encrypted-at-rest replica on hardware you don't fully trust (the "untrusted device" folder type), which makes a friend's NAS a legitimate third location. Two sync systems writing the same directory is a conflict-file factory, per the warnings in both projects' docs.
The other combination worth naming: Syncthing plus a real backup. Sync is not backup — a deletion or ransomware event replicates beautifully. Syncthing's staggered versioning softens this if you enable it, but the actual answer is restic on a 3-2-1 schedule running on whichever node is always on. That pairing, honestly, dissolves most of the file anxiety that sends people to Nextcloud in the first place.
The maintenance bill decides more than features
A year of Syncthing: it updated itself, it synced, a conflict file appeared twice. A year of Nextcloud: three major upgrades (each with a read-the-notes step), PHP version migrations on the host or image, an app or two that lagged a release behind, occasional cron and preview-generation tuning. None of it is hard, but it's a recurring tax, and you should only pay it for features you actually use. The failure mode I see most on r/selfhosted is a household Nextcloud serving one person's sync needs — all bill, no platform benefit.
What I'd do
Just you, multiple devices, "files must exist in more than one place": Syncthing, versioning enabled, conflict sweep in cron, restic underneath — done, and you'll forget it's there. Family or collaborators who need links, logins, calendars, shared albums of documents: Nextcloud, properly provisioned, and accept the maintenance tax with open eyes. Both at once when your working set needs bulletproof replication and other people need windows into it. If you're still unsure, start with Syncthing — it's a 20-minute install with no server commitment, and if you outgrow it, the files are just files, sitting exactly where Nextcloud would want them.