Your .env File Is Lying to You

This video breaks down env vars from the operating system level up — where they live, how they move between processes, and why your app works locally but breaks in Docker. Environment variables aren't a framework feature — they're an OS primitive. Every process on your machine carries its own flat list of key-value strings. We'll walk through the four layers where env vars get set (OS defaults, shell profiles, manual commands, and application tooling like dotenv). Then we get into process inheritance — the reason Docker containers and CI steps don't see your local variables. Finally, we tackle the build-time vs runtime distinction. Timestamps: 0:00 Intro 0:44 What Environment Variables Actually Are 1:33 Where Do They Come From? 3:39 Process Inheritance 5:09 Build-Time vs Runtime 8:30 Recap More Videos : Software Egineering Basics - https://www.youtube.com/playlist?list=PLWP-VtjCVpWyLNBm3zz_sGyC5mVwiAOvj Software Design - https://www.youtube.com/playlist?list=PLWP-VtjCVpWx7kPq30XRN6O6LjVQ4VL95 #environmentvariables #webdev #devops