Docker Compose Port Conflict Checker

How it works

Each pasted file is parsed as YAML with the js-yaml library, then every service's ports list is scanned for host-port mappings — handling short syntax like "8080:80", an IP-prefixed form like "127.0.0.1:8080:80", a trailing "/tcp" or "/udp" protocol suffix, and the long object form ({published, target}) — a bare "80" with no colon is treated as container-only and skipped since it doesn't claim a host port. Any host port claimed by two or more services, whether in the same file or across files, is flagged as a conflict.

FAQ

Does it catch conflicts with ports docker compose picks automatically?

No — it only checks explicit host port mappings you've written in the YAML; container-only ports (with no host side) or ports Docker assigns dynamically aren't claims on a specific host port, so there's nothing to conflict.

Can I check multiple compose files against each other?

Yes — use "Add another file" to paste a second (or third) compose file, and it checks port claims across all of them together, which is useful for catching conflicts between docker-compose.yml and an override file, or between separate stacks meant to run side by side.