Managing Environment Variables in Angular Using --define

Handling environment-specific configurations is crucial in Angular applications, especially when dealing with sensitive data like API keys. Instead of hardcoding values in environment files, we can dynamically inject them at build time using the --define flag.

This approach improves security, avoids exposing sensitive data in the source code, and simplifies deployments across different environments.

Why Use --define for Environment Variables?

Traditionally, Angular provides environment files (environment.ts, environment.development.ts) to manage configurations. However, hardcoding API keys in these files is a security risk.

Instead, using --define allows us to: ✅ Inject environment variables dynamically at build time.
✅ Avoid storing sensitive data in source code.
✅ Easily switch between environments without modifying files.

Project Setup

Our Angular project follows this structure:

src/
├── environments/
│   ├── environment.ts
│   ├── environment.development.ts
├── app/
│   ├── app.component.ts
│   ├── app.component.html
│   ├── app.component.css
│   ├── app.config.ts
│   ├── app.routes.ts
│   ...
├── main.ts
├── index.html
├── styles.css
├── ...

1. Environment Configuration (environment.ts)

Instead of hardcoding values, environment.ts declares the API key variable dynamically:

declare const apiKey: string;

export const environment = {
    apiKey: apiKey
};

Similarly, environment.development.ts follows the same structure, allowing different configurations for development and production.

2. Using Environment Variables in app.component.ts

The API key is retrieved from the environment and used inside app.component.ts:

import { Component } from '@angular/core';
import { environment } from '../environments/environment';

@Component({
  selector: 'app-root',
  templateUrl: './app.component.html',
  styleUrl: './app.component.css'
})
export class AppComponent {
  title = 'ng-env';

  protected readonly apiKey = environment.apiKey;

  constructor() {}
}

Here’s how it works:
✅ environment.apiKey is dynamically assigned at build time.
✅ The API key is used in the component without hardcoding it.

Injecting API Key at Build Time with --define

Instead of modifying environment.ts directly, pass the API key dynamically during the build process:

ng build --define "apiKey='your-secret-api-key-here'"

This replaces apiKey in environment.ts with the provided value, ensuring secure and environment-specific API key management.

Running the Angular Build Locally

Since --define works at build time, you need to first build the project and then serve it using a static server.

1. Build the Project with API Key

Run the following command:

ng build --define "apiKey='your-secret-api-key-here'"

This will generate a production build inside dist/ng-env/browser/.

2. Serve the Built Files Locally

Use npx http-server to serve the built files:

npx http-server dist/ng-env/browser

This starts a local server, and you can access your app at:

🔗 http://localhost:8080 (default port, unless changed)

3. (Optional) Specify a Custom Port

If you want to serve it on a different port, use:

npx http-server dist/ng-env/browser -p 4200

Then, access the app at:
🔗 http://localhost:4200

Why This Approach is Better?

✅ No Hardcoded Secrets – API keys are injected at build time, reducing security risks.
✅ Environment-Specific API Keys – Different keys can be used for different environments dynamically.
✅ Seamless CI/CD Integration – Keys can be injected using CI/CD pipelines (e.g., GitHub Actions, Jenkins).
✅ No Need for Multiple Environment Files – Single environment.ts file works for all environments.

Best Practices

• Ensure API keys are kept secure and not exposed in logs.
• Use CI/CD pipelines to inject secrets dynamically.
• Avoid committing sensitive values in version control (GitHub, GitLab).

Conclusion

By using --define, we can securely manage environment variables in Angular, eliminating the need to store sensitive data in the source code. This approach ensures flexibility, security, and easier deployments across different environments.

Exploring the Code

Visit the GitHub repository to explore the code in detail.

Additional Resources

📚 Angular CLI Environment Configuration
📚 Angular v19 Release Notes

These resources provide deeper insights into environment configuration and the latest Angular features.

That concludes our guide on managing environment variables in Angular! I hope this helps you build more secure and maintainable applications.

Happy coding! 🚀