How to Bridge Networks in Docker Compose (`docker-compose.yml`)

#devops #webdev #programming

Hello, I'm Maneshwar. I'm working on FreeDevTools online currently building **one place for all dev tools, cheat codes, and TLDRs* — a free, open-source hub where developers can quickly find and use tools without any hassle of searching all over the internet.

When running multiple containers in Docker Compos
e, bridging them via a shared network allows them to talk to each other by service name. Here's how to do it right.

What’s a Bridge Network?

A bridge network is the default network driver in Docker. It allows containers to communicate with each other by name.

When you define a custom bridge network in Docker Compose, it:

Keeps your containers isolated
Lets you define aliases and connect external services
Avoids using localhost, which doesn’t work across containers

Setup: A Minimal Example

Let’s say you have a backend (Node.js) and a database (PostgreSQL) and you want them to communicate.

1. `docker-compose.yml`

version: '3.9'

services:
  db:
    image: postgres:16
    environment:
      POSTGRES_USER: user
      POSTGRES_PASSWORD: pass
      POSTGRES_DB: mydb
    networks:
      - backend

  app:
    build: .
    environment:
      DB_HOST: db
    depends_on:
      - db
    networks:
      - backend

networks:
  backend:
    driver: bridge

Here’s what’s happening:

db and app are both connected to the backend bridge network.
app can access the database at db:5432.

Connect to External Networks

Want to connect your service to an external Docker network (maybe created outside Compose)? Do this:

networks:
  backend:
    external: true
    name: my-shared-network

Make sure the external network exists:

docker network create --driver bridge my-shared-network

Use Multiple Networks

You can attach services to more than one network:

services:
  app:
    image: my-app
    networks:
      - backend
      - logging

Then define:

networks:
  backend:
    driver: bridge
  logging:
    driver: bridge

Now app can talk to services in both networks.

Useful Commands

List networks: docker network ls
Inspect a network: docker network inspect <network-name>
Remove a network: docker network rm <network-name>

Testing Connectivity

Use Alpine to test:

docker run -it --network=<network-name> alpine sh
apk add curl
curl http://<service-name>:<port>

Gotchas

Don’t use localhost to connect to other containers. Use the service name.
If two containers aren’t on the same network, they can’t talk.
Compose automatically creates a default network if you don’t define one — but it’s best to be explicit.

Conclusion

Docker Compose + custom bridge networks = clean, isolated, and connected environments.

Define your networks clearly in docker-compose.yml, and your services will behave nicely in any environment.

I’ve been building FreeDevTools.

A collection of UI/UX-focused tools crafted to simplify workflows, save time, and reduce friction in searching tools/materials.

Any feedback or contributors are welcome!

It’s online, open-source, and ready for anyone to use.

👉 Check it out: FreeDevTools
⭐ Star it on GitHub: freedevtools

Let’s make it even better together.

Top comments (2)

Dotallio • Jul 11

Super practical guide! The reminder to avoid localhost and use service names is something I've messed up more times than I want to admit. Do you have any favorite tricks for debugging network issues between containers?