Tips and Tricks #142: Use Multi-Stage Docker Builds for Smaller Images

Reduce container image size by separating build and runtime stages.

Code Snippet

# Build stage
FROM node:20-alpine AS builder
WORKDIR /app
COPY package*.json ./
RUN npm ci
COPY . .
RUN npm run build

# Runtime stage - only production dependencies
FROM node:20-alpine AS runtime
WORKDIR /app
ENV NODE_ENV=production

# Copy only what's needed
COPY --from=builder /app/dist ./dist
COPY --from=builder /app/package*.json ./
RUN npm ci --only=production

USER node
EXPOSE 3000
CMD ["node", "dist/index.js"]

Why This Helps

• Image size reduced by 60-80%
• Faster deployments and pulls
• Smaller attack surface in production

How to Test

• Compare image sizes: docker images
• Verify app runs correctly from final stage

When to Use

Any containerized application. Essential for production deployments.

Performance/Security Notes

Use alpine base images when possible. Don’t include dev dependencies or source code in final image.

References

• https://docs.docker.com/build/building/multi-stage/

Try this tip in your next project and share your results in the comments!