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Syncthing
Continuous file synchronization
System UtilitiesFreeOpen SourceReplaces Dropbox ($12/mo)
Quick Take: Syncthing
4.8
Syncthing is the undisputed king of open-source, private file synchronization. For Mac users who prioritize data sovereignty and privacy over the convenience of 'it just works' cloud ecosystems, it is an essential tool. While it has a steeper learning curve than Dropbox and lacks native iOS integration, its power, flexibility, and 'set and forget' reliability make it a masterpiece of engineering. Once configured, it provides a seamless, invisible bridge between your devices.
Best For
- •Privacy Advocates
- •Developers & Sysadmins
- •Multi-platform Users
Install with Homebrew
brew install --cask syncthingWhat is Syncthing?
Syncthing is a continuous file synchronization program. It synchronizes files between two or more computers in real time, safely protected from prying eyes. Unlike cloud services like Dropbox, iCloud, or Google Drive, Syncthing is fundamentally decentralized. There is no central server that stores your data; instead, your data is yours alone, stored only on the devices you control. Syncthing is open-source software, released under the Mozilla Public License 2.0, and is developed openly on GitHub. Written in Go, it is highly efficient and portable, making it an excellent choice for macOS users, including those on the latest Apple Silicon (M1/M2/M3/M4) Macs, where it runs natively and performantly. Development began in late 2013 by Jakob Borg, and it has since matured into the gold standard for open-source, peer-to-peer (P2P) synchronization. For Mac users, it offers a robust way to keep folders in sync between a MacBook, an iMac, a Linux server, and even Android devices, without relying on third-party cloud storage providers. It handles anything from small text files to large video projects with ease, utilizing a unique Block Exchange Protocol (BEP) to transfer only the parts of files that have changed, saving bandwidth and time. Whether you are a privacy advocate, a developer, or a creative professional, Syncthing provides an encrypted, authenticated, and private way to manage your digital life across multiple devices.
Deep Dive: Syncthing Architecture & Ecosystem
Understanding the engine under the hood reveals why Syncthing is so resilient and efficient compared to traditional syncing methods.
History & Background
Syncthing was released in December 2013 by Jakob Borg. It emerged during the post-Snowden era where digital privacy concerns were peaking. The goal was simple: create a sync tool that was open, decentralized, and secure. Over a decade later, it has maintained a rapid development pace, transitioning from a niche tool to a robust standard used by millions.
How It Works
Syncthing implements the Block Exchange Protocol (BEP). Files are divided into variable-sized blocks (usually 128 KiB to 16 MiB). Each block is hashed using SHA-256. When a file changes, only the modified blocks are transmitted. The system maintains a global model of the directory state in a local LevelDB database. This architecture allows for 'renames' to be handled efficiently without re-downloading data and supports 'pulling' blocks from multiple peers simultaneously, similar to BitTorrent.
Ecosystem & Integrations
Around the core `syncthing` binary, a rich ecosystem has sprung up. On macOS, `syncthing-macos` provides a native wrapper. On Windows, `SyncTrayzor` offers a similar experience. `Mobiüs Sync` bridges the gap to iOS. Additionally, there are community-run Discovery Servers and Relay Servers worldwide, ensuring that the mesh network remains resilient even if official infrastructure experiences downtime.
Future Development
The future of Syncthing focuses on 'Untrusted Devices' encryption improvements, potentially allowing for easier secure backups to untrusted cloud VPS instances. Performance optimizations for massive file counts (millions of files) and improvements to the QUIC protocol implementation (for better connectivity over UDP) are also ongoing priorities.
Key Features
Decentralized P2P Architecture
Syncthing uses a peer-to-peer architecture, meaning no central server holds your data. Devices communicate directly with each other to synchronize files. If two devices are on the same local network, they sync over LAN at high speeds. If they are in different locations, they connect over the internet. This ensures that even if the internet goes down, local sync continues uninterrupted. It also eliminates the single point of failure and privacy risks associated with centralized cloud storage services.
End-to-End Encryption & Authentication
Security is paramount in Syncthing. All communication is secured using TLS (Transport Layer Security). To ensure that only your devices can communicate, Syncthing uses strong cryptographic certificates. Every device is identified by a unique Device ID. When you add a device, you must explicitly allow its ID, ensuring that no intruder can access your cluster. This 'zero-trust' model means even the relay servers used to facilitate connections cannot read your data.
Block Exchange Protocol (BEP)
At the core of Syncthing is the Block Exchange Protocol. Instead of re-uploading an entire file when a small change is made, Syncthing breaks files into blocks. It detects which blocks have changed and transmits only those specific pieces. This makes syncing large files, like virtual machine disk images or 4K video edits, incredibly efficient. It also supports parallel downloads, pulling blocks from multiple devices simultaneously if available.
File Versioning & Data Safety
Syncthing includes a robust versioning system to protect against accidental deletions or ransomware. You can configure versioning per folder, choosing from strategies like 'Trash Can' (keeps deleted files for a set time), 'Simple File Versioning' (keeps the last N versions), or 'Staggered File Versioning' (keeps hourly/daily/weekly backups). This acts as a safety net, allowing you to restore previous versions of files directly from the .stversions folder.
Advanced Ignore Patterns
Power users will appreciate the `.stignore` file, which works similarly to `.gitignore`. It allows you to specify complex patterns to exclude files from synchronization. You can ignore system files like `.DS_Store` on macOS, temporary build artifacts (like `node_modules` or `target/`), or massive caches. This granular control ensures you only sync what matters, saving storage space and bandwidth across your device cluster.
Cross-Platform Compatibility
Syncthing is platform-agnostic. You can sync a folder on your macOS desktop with a Windows laptop, a Linux server, a FreeBSD NAS, and an Android phone. The protocol ensures that file metadata, permissions, and modification times are handled correctly across different operating systems. For Mac users, this bridges the gap between the Apple ecosystem and other platforms seamlessly.
Automatic Network Discovery
Setting up connections is simplified through Global Discovery and Local Discovery. Global Discovery helps devices find each other over the internet using public (or private) discovery servers, without needing static IPs. Local Discovery uses broadcasts to find devices on the same Wi-Fi or LAN instantly. It handles NAT traversal automatically, often requiring no manual port forwarding on your router.
Who Should Use Syncthing?
1The Privacy-Conscious Creative
A graphic designer works on a Mac Studio but travels with a MacBook Air. They refuse to upload client assets to unencrypted clouds like Adobe Cloud or Dropbox due to NDA restrictions. Using Syncthing, they create a 'Current Projects' folder synced between the Studio and Air. When they finish an edit on the Studio, Syncthing instantly pushes the changes to the Air over the LAN. When traveling, the Air syncs changes back via an encrypted tunnel. They use 'Staggered File Versioning' to protect against accidental overwrites of Photoshop files.
2The Full-Stack Developer
A developer uses a MacBook Pro for coding but deploys to a headless Linux home server and a Raspberry Pi. Instead of using Git for temporary config files, environment variables, or large datasets that don't belong in version control, they use Syncthing. They map a 'DevTools' folder across all three machines. A script written on the Mac is immediately available on the Linux server. They use `.stignore` to exclude `node_modules` and `.git` folders to prevent conflicts and save bandwidth.
3The Obsidian Power User
A researcher lives in Obsidian.md for note-taking. They want their 'Second Brain' vault accessible on their iPhone (using Mobiüs Sync, a compatible iOS client), Android tablet, and Mac mini. iCloud is too slow and opaque. They set up Syncthing to sync the markdown vault. The sync is nearly instantaneous. Because Syncthing handles conflict resolution by creating 'sync-conflict' files rather than overwriting, they never lose data if they accidentally edit a note on two devices simultaneously.
4The Home Media Curator
A user has a large collection of family photos and videos on their iPhone and Android phones. They want to back these up to their Mac mini, which acts as a Plex server, without paying for iCloud storage tiers. They install the Syncthing app on Android and Mobiüs Sync on iOS. They configure a 'Camera Upload' folder that acts as a 'Send Only' folder on the phones and 'Receive Only' on the Mac. As soon as they connect to home Wi-Fi, new photos are pushed to the Mac's external RAID drive automatically.
How to Install Syncthing on Mac
Installing Syncthing on macOS is straightforward. You can choose between the command-line version via Homebrew, which is great for background services, or a GUI wrapper application that provides a native Mac menu bar experience.
1
Option A: Install via Homebrew (Recommended for CLI/Service)
Open your Terminal. If you have Homebrew installed, simply run the command `brew install syncthing`. This installs the core binary. To have it start automatically when you log in, run `brew services start syncthing`. This runs Syncthing as a background service managed by launchd.
2
Option B: Install Syncthing for macOS (GUI Wrapper)
Download the 'Syncthing for macOS' DMG from the official GitHub releases page. Drag the application to your Applications folder. When you open it, it will add a Syncthing icon to your menu bar, manage the background process, and provide quick access to the Web GUI and log files. This is often more user-friendly for non-technical users.
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Access the Web Interface
Once installed and running, open your web browser and navigate to `http://127.0.0.1:8384`. This is the local control panel for Syncthing. From here, you will configure your folders, add devices, and manage settings. The first time you access it, you will be prompted to set a username and password for the GUI, which is highly recommended.
Pro Tips
- • If using the Homebrew service, the config lives in `~/Library/Application Support/Syncthing`.
- • The GUI wrapper allows you to easily pause/resume sync from the menu bar.
- • Enable 'Start at Login' in the GUI settings to ensure sync is always active.
Configuration Tips
Establish a robust Identity
Immediately after installation, go to Actions > Settings > General and give your device a recognizable name (e.g., 'MacBook-Pro-M1'). This makes it much easier to identify when pairing with other devices. Also, consider exporting your keys/config if you plan to migrate to a new Mac later.
Master the Ignore Patterns
Before syncing a folder, especially a 'Documents' or 'Code' folder, set up your ignore patterns. Click 'Edit' on the folder, go to the 'Ignore Patterns' tab. Add lines like `*.DS_Store`, `Icon `, and `.Trash-1000`. This prevents macOS system junk from cluttering your other devices, particularly non-Apple ones.
Optimize for Local Discovery
If you mostly sync at home, ensure 'Local Discovery' is checked in settings. This allows devices to find each other via broadcast packets. For the best speed on macOS, ensure your firewall allows the Syncthing binary (incoming connections) so that direct TCP connections can be established, bypassing slower relay servers.
Alternatives to Syncthing
While Syncthing is the open-source champion, several other tools offer file synchronization, each with different trade-offs regarding privacy, ease of use, and cost.
R
Resilio Sync
Formerly BitTorrent Sync, Resilio uses a similar P2P technology but is proprietary software. It is generally faster at transferring massive datasets due to its BitTorrent heritage but locks key features like selective sync behind a paid 'Pro' license.
N
Nextcloud
Nextcloud is a comprehensive self-hosted cloud suite. Unlike Syncthing's decentralized model, Nextcloud requires a central server. It offers more than just file sync (calendars, contacts, office), but is heavier to maintain and relies on the server's uptime.
D
Dropbox / iCloud
The standard consumer choices. They are easier to set up but store your data on third-party servers (not private). They offer 'Smart Sync' (files on demand), a feature Syncthing currently lacks natively without complex workarounds.
Pricing
Free
Syncthing is completely free and open-source software (FOSS). There are no premium tiers, no storage limits (other than your disk space), and no subscriptions. You can use it for personal or commercial use without cost. The project is supported by the Syncthing Foundation via donations.
Pros
- ✓Total Privacy: No data stored on third-party servers.
- ✓No Monthly Fees: Completely free forever.
- ✓Unlimited History: Configurable file versioning.
- ✓LAN Speed: Blazing fast sync on local networks.
- ✓Cross-Platform: Works on Mac, Windows, Linux, Android.
- ✓Open Source: Auditable code and transparent security.
Cons
- ✗No iOS Official App: Must use third-party 'Mobiüs Sync'.
- ✗No 'Files on Demand': Files must fully sync to disk.
- ✗Steeper Learning Curve: Requires understanding of Device IDs.
- ✗Battery Usage: Constant scanning can drain laptop battery.
- ✗Conflict Handling: Manual resolution for sync conflicts.
Community & Support
Syncthing boasts a vibrant and technically literate community. The primary hub is the official forum at `forum.syncthing.net`, where developers and power users are very active in troubleshooting and discussing features. The documentation (docs.syncthing.net) is extensive, covering everything from basic setup to complex firewall configurations and API usage. The source code is hosted on GitHub, where users can report bugs, request features, or contribute code. Because it is a community-driven project, support is peer-to-peer, much like the software itself, but generally high-quality and responsive.
Frequently Asked Questions about Syncthing
Syncthing does not have an official client for iOS due to Apple's file system restrictions and limitations on background processes. However, a third-party app called 'Mobiüs Sync' implements a Syncthing client for iOS. It works well but requires the app to be open or periodic background refreshes to sync effectively.
Our Verdict
4.8/5
Syncthing is the undisputed king of open-source, private file synchronization. For Mac users who prioritize data sovereignty and privacy over the convenience of 'it just works' cloud ecosystems, it is an essential tool. While it has a steeper learning curve than Dropbox and lacks native iOS integration, its power, flexibility, and 'set and forget' reliability make it a masterpiece of engineering. Once configured, it provides a seamless, invisible bridge between your devices.
Best for:Privacy AdvocatesDevelopers & SysadminsMulti-platform Users
About the Author
Productivity & Workflow Analyst
Productivity ApplicationsNote-Taking & Knowledge ManagementTask & Project Management
8+ years in operations management · PMP certified
Related Technologies & Concepts
Block Exchange ProtocolJakob BorgGo (Golang)LevelDBMobiüs SyncPeer-to-Peer
Block Exchange Protocol (The underlying communication protocol used by Syncthing.), Jakob Borg (The original creator and lead maintainer of Syncthing.), Go (Golang) (The programming language Syncthing is written in.), LevelDB (The key-value storage library used for Syncthing's local database.), Mobiüs Sync (A third-party iOS client compatible with Syncthing.), Peer-to-Peer (The network topology used by Syncthing.)
Related Topics
Sources & References
Fact-CheckedLast verified: Feb 15, 2026
Key Verified Facts
- Syncthing was initially released in late 2013.[cite-1]
- Syncthing uses the Block Exchange Protocol (BEP) v1.[cite-2]
- Syncthing is licensed under MPL-2.0.[cite-3]
- 1Syncthing - GitHub Repository
Accessed Feb 15, 2026
- 2Block Exchange Protocol v1 Specification
Accessed Feb 15, 2026
- 3Syncthing License
Accessed Feb 15, 2026
- 4Syncthing macOS Wrapper
Accessed Feb 15, 2026
- 5Mobiüs Sync for iOS
Accessed Feb 15, 2026
Research queries: Syncthing Mac app 2026; Syncthing features macOS