Angular: NG0203: inject() must be called from an injection context such as a constructor, a factory function, a field initializer or a function used with runInInjectionContext

Meaning

inject() only works while Angular is creating something (constructor, field initialiser, provider factory, guards/resolvers). Calling it later, in ngOnInit after async work, in setTimeout, or in plain functions throws NG0203. Inject once as a field and reuse, or run the code in runInInjectionContext.

Common causes

• inject() called inside a method, ngOnInit, a subscribe callback or setTimeout
• Called after an await in an async function
• Used in a plain helper function not invoked during construction
• Test code calling a function that uses inject() outside TestBed.runInInjectionContext
• Called in a module-level variable at import time

Detailed fix by platform

Code examples

@Component({ selector: 'app-x', standalone: true, template: '' })
export class XComponent {
  private http = inject(HttpClient);          // OK: field initialiser
  load() {
    // const router = inject(Router);        // NG0203: not an injection context
    this.http.get('/api').subscribe();
  }
}

How to diagnose

1. Location — Where is inject() called?
2. Timing — After await or in a callback?
3. Tests — Using TestBed.runInInjectionContext?

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