Local browser tool
Port Mapping Explorer
Choose the binding and ports. See the path to the container and copy the YAML fragment. Everything runs in your browser.
Inside your Compose service
ports:
- "127.0.0.1:8080:80/tcp"Between services on the same Compose network, use the service name and internal port, for example app:80.
What this changes
The left port belongs to the host. The right port is where the application must listen inside the container. Changing 8080 to 9090 on the host does not move the application from port 80.
TCP and UDP are different mappings. This tool does not infer an application protocol: a TCP port is not automatically HTTP. IPv6 bindings also require support in the actual container engine and network.
What this tool does not check
It does not check port availability, firewall behavior, container health or whether the application listens on the expected interface. A valid Compose model does not prove runtime reachability. For host-only access, start with a loopback binding and verify the actual deployment.
See the four actual syntax checks →
Docker: ports · Docker: networking · Checked 12 Sep 2026.