I’m trying to understand why SyncThing download speeds are so slow, relative to direct download speeds. I’ve read FAQ and various threads herein.
During download activity…
PC is a dedicated Windows 11 Pro-based PC/server
Seedbox Download Speed max is 50Gbps (shared server)
Local SyncThing: v2.1.2, Windows (64-bit Intel/AMD), Build 2026-06-26
Remote SyncThing: v2.1.0, Linux (64-bit Intel/AMD Container), Build 2026-05-22
SyncThing Connection Type on both ends shows QUIC WAN, NOT Relay
SyncThing Remote Download Speed = 300 KiB/s
Direct download speed from seedbox file browser, for a 7 GB file is approx 40 MB/s
PC Speedtest excellent; connected to router via Ethernet (500 Gbps Internet service)
CPU usage is 23%, fairly steady
30% Memory available
Storage shows limited acticvity (not certain if a bottleneck is still present)
Note, I have htop (Windows) installed, but unfamiliar w/ what/how it may show better performance data
tomasz86
August 3, 2026, 8:15pm
2
Are you getting those speeds when testing downloading a large, single file?
Yes, correct… The same 7 GB file I can easily direct download. BTW, that file is still downloading via SyncThing 4.5 hrs later, no other activity on PC, ie no downloading, no playing media, etc.
xor-gate
August 6, 2026, 4:29am
4
Do you have direct-connect or via relay server ? Like in Syncthing ports NAT-unfirewalled and port-forwarded? At least one of the two machines needs to see each other over the internet. Or else you use a relay server which can be rate-limited.
For firewall configuration see Firewall Setup — Syncthing documentation but probably you already tweaked it. And you are using IPv4 or IPv6 ?
My connection appears to be proper. Per my notes above, my connection is NOT indicated as Relay.
IPv4/IPv6: I do have both available, tho according to the console log, looks like IPv6…
INF QUIC listener starting (address="[::]:22000" log.pkg=connections)