Configuration with @nestjs/config

The ConfigModule loads environment variables and exposes them through an injectable ConfigService.

Syntaxthis.configService.get('KEY')

Hard-coding secrets and settings is a mistake. The @nestjs/config package loads values from .env files and environment variables and serves them through a ConfigService.

Setup

  1. Import ConfigModule.forRoot() in the root module. Add isGlobal: true so you can inject ConfigService anywhere.
  2. Inject ConfigService and read values with get().

Keep a .env file out of version control and provide a .env.example template instead.

Example

Example · typescript
import { Module } from '@nestjs/common';
import { ConfigModule, ConfigService } from '@nestjs/config';

@Module({
  imports: [ConfigModule.forRoot({ isGlobal: true })],
})
export class AppModule {}

// Anywhere with DI:
// constructor(private config: ConfigService) {}
// const port = this.config.get<number>('PORT');

When to use it

  • A developer loads database credentials from a .env file using ConfigModule.forRoot() so the app never hard-codes secrets.
  • A team uses a Joi validation schema in ConfigModule.forRoot({ validationSchema }) to fail fast at startup if required env vars are missing.
  • An engineer injects ConfigService into a service and calls cfg.get<number>("PORT", 3000) to read typed config values with a safe default.

More examples

Load .env with ConfigModule

Registers ConfigModule as a global module that reads the .env file, making ConfigService injectable everywhere without repeated imports.

Example · ts
import { Module } from '@nestjs/common';
import { ConfigModule } from '@nestjs/config';

@Module({
  imports: [
    ConfigModule.forRoot({
      isGlobal: true,   // no need to import in every module
      envFilePath: '.env',
    }),
  ],
})
export class AppModule {}

Inject ConfigService

Injects ConfigService and reads DATABASE_URL with a fallback default, using TypeScript generics for a typed return value.

Example · ts
import { Injectable } from '@nestjs/common';
import { ConfigService } from '@nestjs/config';

@Injectable()
export class AppService {
  constructor(private config: ConfigService) {}

  getDatabaseUrl(): string {
    return this.config.get<string>('DATABASE_URL', 'sqlite::memory:');
  }
}

Validate env vars with Joi

Passes a Joi schema to ConfigModule so the app throws an error at startup if any required environment variable is missing or invalid.

Example · ts
import * as Joi from 'joi';

ConfigModule.forRoot({
  isGlobal: true,
  validationSchema: Joi.object({
    DATABASE_URL: Joi.string().uri().required(),
    JWT_SECRET:   Joi.string().min(32).required(),
    PORT:         Joi.number().default(3000),
  }),
})

Related

nest dynamic modulesnest deployment

Discussion

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