A container app will not open
Check app startup, published ports, HTTP or HTTPS, dependencies, and Tailscale routes when a running container is unreachable.
A running container can still be waiting for its app to start. Follow these checks when its page times out, refuses the connection, or shows an app error. For a stopped container, start with A container will not install or start.
Check the app's startup
Open the container's Logs and look for the app's listening address or startup error. Complete the catalog's Install instructions, including any first-run setup. If the app needs a database or another service, check that dependency's logs too.
For separately installed catalog dependencies, use the Mac's IP and the dependency's published
port as described in App Store.
localhost inside a container points to that container. Check credentials and required
environment variables without changing or deleting its data volume.
Match the address to the published port
Open the container's details and compare its published ports with the port the app listens on.
From another LAN device, use the Mac's IP and the host port. For example, a mapping from
host 8080 to container 80 opens at http://your-mac-ip:8080.
The Run form's Host IP restricts which address accepts connections. Blank publishes on
every address; 127.0.0.1 accepts connections from the Mac only. Use Edit → Save & recreate
to change a mapping, briefly interrupting the app.
The container's Address and Open in its detail panel, and Open URL in its row menu, use the container's own IP and the container port. Another device reaches that address only with a route to the container network. Start with the Mac's published port for LAN access.
Check the protocol
Use the HTTP or HTTPS scheme required by the app. Udon builds links using HTTPS for ports 443 and 8443 and HTTP for other ports; an app using a different arrangement may need its address entered manually.
The install dialog lists published TCP ports under Access. UDP-only services do not get a browser link, and a TCP service such as a database still needs its own client.
Check remote container access
First confirm the same app address works from the Mac or LAN. For Tailscale, use the Mac's Tailscale address and published host port. Serve with a trusted certificate publishes Udon's dashboard; it does not publish every container app.
To use a container's own IP, enable Advertise the container network in
Settings → Tailscale and approve the route in the Tailscale admin console. Compare the
displayed subnet with the container network. Udon infers a /24 or falls back to Apple's
default subnet. If it differs, use published ports and include both subnets in a support
request. See Network & remote access.
Confirm recovery by opening the app from the device that originally failed. If it still fails, email [email protected] with the engine, image/tag, port mapping, tested address, browser error, and relevant startup logs. Remove credentials and tokens before sending.