Icon could not be downloaded from the given URL #1609

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1. LinuxServer-CI

   added this to Issue & PR Trackeron Oct 5, 2026
2. KodeStar commented on Oct 18, 2026

   

   KodeStar

   on Oct 18, 2026

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   Thanks for the report. There are two separate problems here.

   SVG upload rejected ("The file field must be an image."): I can reproduce this. It is a bug and is fixed in #1612, which will ship in the next release. Until then, your PNG workaround is the way to go.

   "Icon could not be downloaded from the given URL.": when you pick an application type, the icon preview loads in your browser, but on save Heimdall downloads the icon again from inside the container (https://appslist.heimdall.site/icons/homeassistant.svg). That server-side download is what fails here. I couldn't reproduce it with a stock lscr.io/linuxserver/heimdall:2.8.3 container, so it looks like something about the container's network. Could you send:

   1. The output of this, run on the Docker host (replace heimdall with your container name):

      docker exec heimdall curl -sSI https://appslist.heimdall.site/icons/homeassistant.svg
      

   2. Any lines mentioning Outbound request from today's log in /config/www/logs/laravel-YYYY-MM-DD.log (in your mapped config folder), taken right after a failed save.
   3. Whether the container uses a proxy (HTTP_PROXY/HTTPS_PROXY), a custom DNS server, or a restricted Docker network.
   4. Whether adding an application type worked for you on 2.8.2 or earlier.
3. GustelDE commented on Oct 18, 2026

   

   GustelDE

   on Oct 18, 2026

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   Hello, executed from inside the container it throws this:
   

   In a regular Linux-VM this is the output:
   

   Was digging further, it seems appslist.heimdall.site is a CNAME of linuxserver.github.io:
   

   Somehow the container is querying IPv6 (AAAA) to resolve "linuxserver.github.io", which is blocked by my PiHole:
   

   Gemini told me to add this to my docker-compose.yaml:
   sysctls:
   - net.ipv6.conf.all.disable_ipv6=1

   Now it works. Not sure why it started using IPv6 for DNS. But okay :)

   
4. KodeStar commented on Oct 19, 2026

   

   KodeStar

   on Oct 19, 2026

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   Thanks for digging into that, nice find. That confirms the download error comes from the network rather than Heimdall: your Pi-hole is answering IPv6 lookups for linuxserver.github.io with an address that points at a different server, so anything in the container that prefers IPv6 ends up there. A cleaner fix than disabling IPv6 in the container is to allowlist linuxserver.github.io in Pi-hole, so other containers aren't affected either.

   The SVG upload problem is fixed in #1612 and will be in the next release. Closing this one, but feel free to reopen if anything comes back after updating.
5. KodeStar

   closed this as completedon Oct 19, 2026
6. LinuxServer-CI

   moved this from Non-Docker Issues to Done in Issue & PR Trackeron Oct 19, 2026