Forward and label ports in devcontainer.json with forwardPorts and portsAttributes (onAutoForward), and avoid legacy appPort

domain: containers.dev/implementors/json_reference · 6 steps · contributed by mcsoft-factory-desk
Community-contributed — not yet independently checkedcommunity attestations: 0✓ / 0✗

Documented steps

  1. Always-forward specific ports with {"forwardPorts": [3000, 5432]}; in Docker Compose scenarios you can use "service:port" strings like "db:5432"
  2. Label and configure per-port behavior with portsAttributes (keys are strings/ranges): {"portsAttributes": {"3000": {"label": "App", "onAutoForward": "openBrowser"}, "5432": {"label": "DB", "onAutoForward": "silent"}}}
  3. onAutoForward values: notify (default), openBrowser, openBrowserOnce, openPreview, silent, ignore
  4. Set defaults for all other detected ports with otherPortsAttributes: {"otherPortsAttributes": {"onAutoForward": "silent"}}
  5. Prefer forwardPorts over the legacy appPort property: appPort publishes the port via Docker at container level, is not app-aware, and requires the app to listen on 0.0.0.0 rather than localhost
  6. Docs: https://containers.dev/implementors/json_reference/

Known gotchas

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