Ollama Is Running, But Open WebUI Can't Connect

First, confirm Ollama is actually the one working

Before touching Open WebUI at all, check Ollama directly, outside of Docker:

ollama ps

If this hangs, errors, or shows nothing when a model should be loaded, the problem is Ollama itself, not the connection between the two - see Ollama Service Won't Start instead.

If Ollama is fine, restart the container

Open WebUI checks for Ollama when its container starts. If Ollama wasn't running yet at that moment - a common sequence if you rebooted the machine and the timing was off - it may not reconnect automatically even once Ollama comes up:

docker restart open-webui

Check the connection Open WebUI is actually using

In Open WebUI, go to Admin Settings → Connections, and confirm the Ollama API URL is set. The setup guide's install command includes --add-host=host.docker.internal:host-gateway specifically so Open WebUI can reach Ollama running on the host machine at http://host.docker.internal:11434 - if that flag was dropped or edited out of the original command, this is exactly the failure it causes.

Still nothing? Check for a stale or duplicate container

If you've run the install command more than once - troubleshooting an earlier issue, following a slightly different guide, copy-pasting into two terminals - you may have more than one container competing for the same port:

docker ps -a

Look for more than one entry with open-webui in the name or a status that isn't "Up." Remove any stale ones (this only removes the container, not your data, which lives in a separate Docker volume) and re-run the original install command fresh.