Docker Multi-Stage Builds: How to Create Smaller, Cleaner Container Images

Docker's multi-stage build feature allows developers to separate the build environment from the final production image, resulting in significantly smaller container sizes. In a standard single-stage Python Dockerfile, unnecessary tools like pip cache and build utilities are included in the final image, adding unwanted bulk. By splitting the Dockerfile into two stages, the first stage handles dependency installation while the second copies only the essential files needed to run the application. The size advantage is even more pronounced with compiled languages like Go, where the final image can be built from scratch containing nothing but the compiled binary. A recommended best practice is to name each stage using the AS keyword — such as builder, test, or dev — to improve Dockerfile readability and maintainability.