Files and storage, checked 2026-09-07
Syncthing: Docker configuration reference
Continuous, peer-to-peer file synchronization between two or more devices without a central server.
At a glance
Ports
Ports| Port | What listens | Source |
|---|
8384 | GUI and REST API. Bound to 0.0.0.0 by default inside the container so it is reachable without host networking; the config's own GUI Listen Address falls back to 127.0.0.1 if STGUIADDRESS is unset. | source for port 8384 |
22000 | Sync protocol, both TCP (direct connections) and UDP (QUIC). | source for port 22000 |
21027 | UDP local discovery broadcasts (IPv4) and multicasts (IPv6). Only needed for LAN auto-discovery. | source for port 21027 |
Environment variables
Environment variables| Variable | Required | What it does | Example | Source |
|---|
PUID | No | UID Syncthing runs as inside the container. Defaults to 1000; set to match the owner of the mounted sync folder. | 1000 | source for PUID |
PGID | No | GID Syncthing runs as, alongside PUID. | 1000 | source for PGID |
STGUIADDRESS | No | Overrides the GUI bind address baked into the image. Unset it (empty value) to fall back to whatever is configured in config.xml or the GUI itself. | 0.0.0.0:8384 | source for STGUIADDRESS |
PCAP | No | Grants additional Linux capabilities without running the container as root, using setcap(8) syntax. | cap_chown,cap_fowner+ep | source for PCAP |
Volumes that must persist
Volumes| Path | What is in it | Source |
|---|
/var/syncthing | Config, database and the default location for synced folders. Everything Syncthing needs to keep working across a redeploy. | source for /var/syncthing |
Behind a reverse proxy
- The official image recommends network_mode: host for the sync ports, because Docker's default bridge network hides devices' real LAN addresses and breaks direct LAN transfers. source for this reverse-proxy note
- The GUI on 8384 can still be reverse-proxied normally; only the sync protocol ports benefit from host networking. source for this reverse-proxy note
- If the GUI is made externally reachable, enable GUI authentication and TLS first; STGUIADDRESS alone does not add either. source for this reverse-proxy note
- Port forward 22000/TCP and 22000/UDP (or the custom Sync Protocol Listen Address port) for devices behind NAT to connect directly instead of falling back to a relay. source for this reverse-proxy note
Release timeline
Releases| Version | Date | Breaking | What changed | Source |
|---|
v2.1.3 | 2026-08-05 | No | Part of the 2.1 line: devices and folders can be grouped in the GUI, and HTTP/HTTPS CONNECT proxies are now supported alongside SOCKS. | source for release v2.1.3 |
v2.1.2 | 2026-07-08 | No | 2.1 line maintenance release. | source for release v2.1.2 |
v2.1.1 | 2026-06-02 | No | 2.1 line maintenance release: same major changes as 2.1.0, including GUI device/folder grouping and CONNECT proxy support. | source for release v2.1.1 |
If it is not coming up
Read from the upstream documentation, repository and container registry by Keita Emsden on 2026-09-07. Every row links the page it came from. Upstream changes without telling anyone, so check the source link before you rely on a value.
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