Base URL of Portainer. Do not include /api or a path.

Use the API listen address (same host that serves /api/…), not a separate UI-only vhost.

Typical Portainer ports: 9000 (HTTP) or 9443 (HTTPS). Port 80/443 only if you terminate TLS/proxy there on purpose.

Example:

https://portainer.example:9443

Must be http:// or https://. Do not put credentials in the URL.