When trying to create the file, the frontend receives a response without the Location header and retries, resulting in a status 409. It appears that you're using a proxy that omits the Location header because it contains an empty value, but this header is still essential for the application. Can you provide some details of your proxy configuration so I can determine whether this should be addressed by File Browser itself?

@ramiresviana is it maybe possible to do this without relying on an empty header?

@hacdias after some experimentation, I discovered that we can use a dummy value instead of leaving it empty. By using a value like #upload, which is an URI fragment, the frontend will ignore it when constructing the upload URL. What do you think?

Good catch; reverse proxy is a barebone lighttpd/1.4.79. Snippet of lighttpd config:

$SERVER["socket"] == ":443" {
  $HTTP["url"] =~ "^/file" {
      proxy.server = ( "" => (( "host" => "127.0.0.1", "port" => "8081" )))
  }
}

along with relevant part of filebrowser config:

{
    "server": {
        "address": "127.0.0.1",
        "baseurl": "/file/",
        "port": "8081",
    },
}

Lighttpd has worked fine for this and other services for a very long time though; if it's possible not to break compatibility, it would be grand.

@ramiresviana see here: #5302

Fix confirmed, thank you!