Open source alternative to Resilio Connect, Dropbox and Tresorit
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A continuous file synchronization tool that securely syncs files across devices in real-time.
Syncthing runs as a background service on a NAS or home server and keeps multiple computers in sync over the local network and internet without a cloud subscription. After the initial pairing, it operates unattended and handles file conflicts gracefully.
You need to access files from a browser on any device without installing Syncthing, or you rely on iOS for mobile access and need background sync.
Teams sharing design assets, media files, or compiled artifacts can sync directly between machines without committing large binaries to git. Send-only and receive-only modes support one-way distribution of shared assets from a central machine to team members.
You need real-time collaborative editing or a shared file system with version history, comments, and fine-grained per-user permissions. Syncthing moves files; it does not provide a document collaboration layer.
Users who do not want cloud providers storing their personal files get continuous encrypted sync between their own devices with no third-party server involved. There are no paid tiers, no terms of service granting provider access to content, and no usage data sent externally.
You regularly access files from shared or borrowed computers where you cannot install software, or you rely on public link sharing from your sync service.
Syncthing's receive-only mode lets a primary machine push configuration files, scripts, or static assets to remote servers over the internet without giving those servers write access back. It authenticates by device ID rather than passwords, and all data is encrypted in transit.
Your infrastructure already uses a configuration management tool like Ansible or Puppet. Syncthing adds lightweight continuous distribution; it does not handle state enforcement, rollback, or dependency ordering.
Cloud sync services put your files on servers controlled by a vendor. You pay monthly fees for storage the provider can discontinue, and you accept terms of service that give the vendor access to your content for abuse detection, compliance checks, or model training. Free tiers cap at 2-15GB, while professional plans for larger teams run $10-20 per user per month. When a provider raises prices or suspends an account, you have little recourse.
The deeper problem is that cloud sync is not ownership. You can lose access to your own files if a payment fails, an account is flagged, or a service shuts down. For developers, photographers, and small teams syncing sensitive work, trusting a third party with unrestricted access to files is not a tradeoff worth making. A sync tool that stores data only on your own hardware eliminates the vendor as a failure point entirely.
Syncthing transfers files directly between your devices without routing data through a cloud server. Discovery happens automatically on the local network or over the internet via an encrypted relay fallback. Your files never touch Syncthing's infrastructure; relay servers used for difficult NAT traversal see only encrypted blocks.
Every device connection uses TLS with perfect forward secrecy. Each Syncthing instance generates a unique cryptographic certificate on first run, and you must explicitly approve each device ID on both ends before any sync begins. This prevents unauthorized devices from joining your sync network even if they know your device ID.
Each folder can be shared selectively with specific devices and set to send-only, receive-only, or bidirectional mode. A folder shared with a work laptop does not have to sync to a phone. Receive-only mode lets a device mirror files from a trusted source without being able to push changes back.
Syncthing runs a local web UI at port 8384 for configuration, device management, and sync monitoring. You can check connected peers, current transfer rates, folder health, and recent changes from a browser without installing a native desktop client. The REST API is also available for scripting and automation.
Pre-built binaries run on Windows, macOS, Linux, FreeBSD, Solaris, and OpenBSD across x86-64, ARM64, and other architectures. It ships as a single Go binary with no runtime dependencies. Android is supported via the community Syncthing-Fork app; iOS support is limited due to OS background processing restrictions.
Both tools keep files in sync across multiple devices, but they use fundamentally different architectures. Syncthing syncs files directly between your devices with no central server; Dropbox routes all files through its cloud infrastructure, where they are stored on Dropbox-managed servers.
| Feature | Syncthing | Dropbox |
|---|---|---|
| License | MPL-2.0 (open source) | Proprietary |
| Storage location | Your own devices | Dropbox cloud servers |
| Storage limit | Local disk only | 2GB free, paid from $10/user/month |
| Self-hosting | Yes | No |
| iOS support | Limited (no background sync) | Full |
| Web file access | No (requires companion tool) | Yes (browser portal) |
Syncthing is the better choice when data ownership matters: your files never leave your machines, there is no vendor that can be breached or subpoenaed, and there is no storage fee. It is also the right call when syncing large volumes of data that would be expensive under a cloud subscription.
Dropbox is still the better fit when you need reliable iOS background sync, access files from browsers on machines where Syncthing is not installed, or share public links to individual files with people outside your organization. Dropbox's mobile apps and web interface are more polished and require no server-side setup.
Nextcloud is the most common alternative when users outgrow Syncthing and want additional collaboration features. Nextcloud provides file sync plus a web interface, document editing, calendar, contacts, and team sharing, all self-hosted.
| Feature | Syncthing | Nextcloud |
|---|---|---|
| Primary function | Peer-to-peer file sync | Self-hosted cloud platform |
| Setup complexity | Low (single binary) | Moderate (web server, PHP, database) |
| iOS sync | Limited | Full (official Nextcloud app) |
| Web file access | No | Yes |
| Additional apps | Sync only | Calendar, contacts, docs, and more |
Syncthing is the right pick when you want simple, lightweight, reliable sync with no server infrastructure overhead. Nextcloud is the right pick when you need a web portal, full iOS and Android sync, team sharing with permissions, or additional productivity apps.
```bash
# Debian / Ubuntu (stable apt repo)
sudo mkdir -p /etc/apt/keyrings
sudo curl -L -o /etc/apt/keyrings/syncthing-archive-keyring.gpg https://syncthing.net/release-key.gpg
echo "deb [signed-by=/etc/apt/keyrings/syncthing-archive-keyring.gpg] https://apt.syncthing.net/ syncthing stable-v2" | sudo tee /etc/apt/sources.list.d/syncthing.list
sudo apt-get update && sudo apt-get install syncthing
```
```bash
# Docker (host network mode required for LAN discovery)
docker run --network=host \
-e STGUIADDRESS= \
-v /wherever/st-sync:/var/syncthing \
syncthing/syncthing:latest
```
```yaml
# Docker Compose
services:
syncthing:
image: syncthing/syncthing
container_name: syncthing
environment:
- PUID=1000
- PGID=1000
volumes:
- /wherever/st-sync:/var/syncthing
network_mode: host
restart: unless-stopped
```
# After install, web UI is available at http://localhost:8384For users who want files on their own devices without a cloud middleman, yes. Syncthing keeps files in sync across your devices over an encrypted P2P connection, with no storage fees and no cloud server involved. The main differences are that Syncthing does not provide a web portal for accessing files from any browser, and iOS support is limited to apps that sync only while open. For desktop-to-desktop or desktop-to-NAS sync, it is a strong Dropbox replacement.
Yes. Syncthing is free and open source under the MPL-2.0 license. There is no paid plan, no storage subscription, and no account required. The only cost is the hardware you install it on.
No. Syncthing is a sync tool, not a backup tool. Any file you delete or overwrite on one device will have that change propagated to all other connected devices. For data protection, use a dedicated backup tool such as Restic, Borg, or Duplicati alongside Syncthing.
Syncthing uses a global discovery server to allow devices to find each other by device ID. If a direct connection is not possible due to NAT or firewall restrictions, Syncthing routes transfers through relay servers that see only encrypted data. You do not need to configure port forwarding or know the remote device's IP address.
No. Your files are transferred directly between your devices. Syncthing's public infrastructure handles only device discovery lookups and encrypted relay traffic; no file content passes through or is stored by the Syncthing project's servers.
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