How do you reduce Docker image size?

Smaller images are faster to build, push, pull, and have a smaller attack surface. Strategies: (1) Use minimal base images: prefer alpine variants (node:20-alpine ~50MB vs node:20 ~350MB); for compiled languages, use scratch (empty) or distroless images; (2) Multi-stage builds: separate build tools from runtime — only copy the built artifacts to the final stage; (3) Combine RUN instructions: each RUN creates a layer — combine commands with && to reduce layers and clean up in the same step: RUN apt-get update && apt-get install -y curl && rm -rf /var/lib/apt/lists/* — the cleanup is in the same layer and actually reduces size; (4) Remove caches and temp files: for apt: rm -rf /var/lib/apt/lists/*; for npm: npm ci --only=production or npm cache clean --force; (5) Use .dockerignore: exclude node_modules, .git, tests, docs; (6) Avoid unnecessary packages: don't install debugging tools in production images; (7) Use COPY instead of ADD; (8) Pin specific versions not :latest; (9) Analyze with dive tool (visualizes layers and wasted space) or docker image history myimage.