Learn how to hide API keys using Node.js and dotenv environment variables in this comprehensive tutorial. Discover how to set up a Node.js API key relay to securely access API data while protecting sensitive information. Follow along as the instructor guides you through installing Node.js, setting up package dependencies, creating an API, implementing weather routes, and adding environment variables. Explore techniques for testing routes, implementing rate limiting, and protecting your application. Gain insights into proper use of .gitignore files and deploying your code to platforms like Glitch. By the end of this tutorial, you'll have the knowledge to create secure server-side applications that safeguard API keys while maintaining functionality.