ExposeInvalidFormat - Docker

Output

text

EXPOSE instruction should not define an IP address or host-port mapping, found '127.0.0.1:80:80'

Description

The EXPOSE instruction in a Dockerfile is used to indicate which ports the container listens on at runtime. It should not include an IP address or host-port mapping, as this is not the intended use of the EXPOSE instruction. Instead, it should only specify the port number and optionally the protocol (TCP or UDP).

[!IMPORTANT] This will become an error in a future release.

Examples

❌ Bad: IP address and host-port mapping used.

dockerfile

FROM alpine
EXPOSE 127.0.0.1:80:80

✅ Good: only the port number is specified.

dockerfile

FROM alpine
EXPOSE 80

❌ Bad: Host-port mapping used.

dockerfile

FROM alpine
EXPOSE 80:80

✅ Good: only the port number is specified.

dockerfile

FROM alpine
EXPOSE 80