Why Your Docker Images Are So Big (And How to Fix It)

10/9/2025

Complete 3-part series on Docker image optimization. Learn why images become bloated and discover practical techniques to reduce image size by 80% or more.

Why Your Docker Images Are So Big (And How to Fix It)

Ever wondered why your Docker images are taking forever to build and deploy? You’re not alone. Bloated Docker images are one of the most common problems in containerized applications.

In large scale CI/CD pipelines, bloated images can waste hours of compute time and gigabytes of storage per build. Let’s fix this once and for all.

Complete 3-Part Series

This comprehensive guide has been split into 3 focused posts for better learning and reference:

Part 1: The Problem & Real Example

6 min read | Understanding the issues and seeing real comparisons

• The problem with bloated Docker images
• Real-world Flask application example
• Size comparisons: Ubuntu vs Slim vs Alpine
• Python base image decision matrix
• Which base image to choose for Python apps

Part 2: 7 Essential Techniques

8 min read | Core optimization strategies you can implement today

• Choose the right base image
• Multi-stage builds
• Combine RUN commands
• Use .dockerignore
• Remove package managers
• Copy only what you need
• Use distroless images
• Best practices checklist

Part 3: Advanced Techniques & Tools

6 min read | Expert-level optimization and powerful analysis tools

• Layer caching optimization
• BuildKit for faster builds
• Build arguments for conditional installs
• Health checks
• Analysis tools: Docker History, Dive, Docker Slim
• Testing your optimizations
• Advanced best practices

What You’ll Learn

By the end of this series, you’ll be able to:

• Reduce image sizes
• Help choose the right base image for your application
• Implement multi-stage builds for complex applications
• Use powerful analysis tools to identify optimization opportunities
• Set up automated optimization in your CI/CD pipeline
• Avoid common mistakes that bloat your images

Additional Resources

• Docker Best Practices
• Alpine Linux Packages
• Distroless Images
• Dive Tool Documentation
• Docker Slim Documentation

Ready to optimize your Docker images? Start with Part 1: The Problem & Real Example and work your way through the series!