Docker Multi-Stage Build Generator

A multi-stage Docker build uses multiple FROM instructions in one Dockerfile. Each stage can use a different base image and selectively copy artifacts to the next stage. The key benefit: your final production image only contains the compiled output — not build tools, source code, or dev dependencies. A typical Node.js app can shrink from 1+ GB (with node_modules and build tools) to under 100 MB. Go apps can use the scratch base image, producing images under 10 MB.

Results vary by language and app, but typical gains are significant: Node.js apps go from ~1 GB (full node:22) to ~150-300 MB with node:22-alpine + multi-stage. Go apps using scratch can be under 20 MB since the binary is statically linked. Python apps reduce by 40-60% by excluding pip cache and build tools. Rust apps with debian:bookworm-slim production stage typically yield 50-100 MB final images compared to 2+ GB build images.

node:22-alpine uses Alpine Linux (~5 MB base) with musl libc — extremely small but may have compatibility issues with native npm modules that expect glibc. node:22-slim uses Debian Bookworm Slim with glibc — larger (~200 MB) but compatible with all npm packages including native addons (bcrypt, sharp, canvas). Use alpine when you have no native modules; use slim when you need glibc compatibility.

Go compiles to a statically-linked binary with CGO_ENABLED=0, meaning it has zero runtime dependencies — no OS libraries needed. FROM scratch is a completely empty Docker layer. The only files needed are the binary and SSL certificates (for HTTPS requests). This produces the smallest possible image and the smallest attack surface. If your Go binary uses CGO or dynamic linking, switch the production stage to FROM debian:bookworm-slim or FROM alpine instead.