ghostfolio/.agents/skills/angular-developer/references/environment-configuration.md

Environment configuration

Configuration strategies

Angular supports two main configuration strategies:

• Build-time configuration using environment files
• Runtime configuration by loading values at application startup

Choose the approach based on your deployment requirements.

---

Build-time configuration

Environment files define configuration values that are replaced at build time.

Security note: Environment files are bundled into the client-side application. They are visible to anyone who can load the page. Never store sensitive information like API keys, secrets, or credentials in environment files. These values can be easily accessed by users.

Generate environment files using the CLI:

ng generate environments

This creates environment-specific files such as:

// environment.ts
export const environment = {
  apiUrl: 'https://api.example.com',
};

// environment.development.ts
export const environment = {
  apiUrl: 'http://localhost:3000',
};

Import the environment where needed:

import {environment} from '../environments/environment';

const apiUrl = environment.apiUrl;

The Angular CLI replaces the appropriate file based on the build configuration.

If you need a development-mode check, use isDevMode() from @angular/core instead of relying on a manually maintained production flag.

Changes to environment files require rebuilding the application.

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Runtime configuration (advanced)

In some scenarios, applications need to load configuration at runtime instead of build time.

This allows the same build artifact to be deployed across multiple environments without rebuilding.

A common approach is to load a JSON configuration file from the assets folder during application initialization.

Example

// src/assets/config.json
{
  "apiUrl": "https://api.example.com"
}

Load the configuration before the application starts:

import {Service, inject} from '@angular/core';
import {HttpClient} from '@angular/common/http';

@Service()
export class AppConfigService {
  private config!: {apiUrl: string};

  private readonly http = inject(HttpClient);

  loadConfig() {
    return this.http.get<AppConfig>('/assets/config.json').pipe(
      tap((data) => {
        this.config = data;
      }),
    );
  }

  get apiUrl(): string {
    return this.config.apiUrl;
  }
}

Register the loader during application bootstrap:

import {provideAppInitializer, inject} from '@angular/core';

provideAppInitializer(() => {
  const config = inject(AppConfigService);
  return config.loadConfig();
});

This ensures configuration is available before the application renders.

Runtime configuration is an advanced pattern and is not required for most applications.

---

Choosing a strategy

Criteria	Build-time	Runtime
Change without rebuild	No	Yes
Startup performance	Faster	Slight delay
Complexity	Low	Moderate
Deployment flexibility	Limited	High

Use build-time configuration for most applications, and runtime configuration when you need to deploy the same build across multiple environments.