midDocker
Difference between 'COPY' and 'ADD' in a Dockerfile.
Updated Apr 28, 2026
Short answer
COPY is for basic file copying; ADD has extra features like remote URL support and automatic tar extraction.
Deep explanation
Modern Docker workflows focus on optimization. Multi-stage builds allow you to use a heavy build environment (with compilers and tools) but only copy the final binary into a slim production image (like Alpine).
Real-world example
Running a WordPress site with separate containers for PHP-FPM, Nginx, and MySQL locally.
Common mistakes
- Storing sensitive passwords in plain text within the Dockerfile or environment variables.
Follow-up questions
- How does Docker networking work by default?