Why Multi-stage builds concept in Docker? - Purpose & Use Cases

The Big Idea

What if you could build your app and deliver a tiny, clean image without messy manual cleanup?

The Scenario

Imagine you want to create a small, fast Docker image for your app, but your app needs many tools to build. You first install all tools, build the app, then try to remove the tools manually before sharing the image.

The Problem

This manual way is slow and messy. You might forget to remove some tools, making the image big and slow to download. Also, cleaning up by hand is error-prone and wastes time.

The Solution

Multi-stage builds let you use one Dockerfile to build your app in one stage with all tools, then copy only the final app to a clean, small image in the next stage. This keeps images tiny and build steps clear.

Before vs After

✗ Before

FROM ubuntu
RUN apt-get update && apt-get install -y build-essential
RUN build-app
RUN apt-get remove -y build-essential
CMD ./app

✓ After

FROM ubuntu AS build
RUN apt-get update && apt-get install -y build-essential
RUN build-app
FROM scratch
COPY --from=build /app /app
CMD ["/app"]

What It Enables

It enables creating small, efficient Docker images by separating build and runtime environments cleanly.

Real Life Example

Developers building a Go app use multi-stage builds to compile the app with all tools, then produce a tiny final image with just the compiled binary, perfect for fast deployment.

Key Takeaways

Manual cleanup of build tools is slow and error-prone.

Multi-stage builds separate build and runtime steps in one Dockerfile.

Final images become smaller, faster, and easier to manage.