Very slow download/upload speed through the browser

I’m having some strange performance issues with uploading and downloading on nextcloud via browser. I had two friends test downloading a 2GB file, and the average speed was about 200KB/s.

For reference, my upstream speed is 20-30Mb/s, so I’m not even close to hitting that limit.

I’m getting even worse slowdowns with uploading, around 30KB/s from the client side. (my downstream speed is around 500Mb/s)

This issue doesn’t seem to be present using the desktop app, so something’s definitely misconfigured. Does anyone have any suggestions or know what the problem might be?

BTW for reference, NC is installed as a TrueNAS jail, with NGINX proxy manager for the reverse proxy. I’ve also tried disabling hardware offloading on the network interface in truenas, as well as adjusting the MTU.


The desktop app is using parallel uploads for large files. I’d try a direct webdav connection (winSCP or some other client that supports webdav directly). I’d try to check if there is a difference depending on file size.
Check the logs of the webserver/php/nextcloud, also resource usage…