[Solved] You have an Angular service declared as:@Injectable() export class AuthService {}What issue arises if you want this service to be a singleton but do not specify providedIn or add it to a module's... | Angular

Angular - Services and Dependency Injection

You have an Angular service declared as:

@Injectable()
export class AuthService {}

What issue arises if you want this service to be a singleton but do not specify providedIn or add it to a module's providers?

AAngular will not provide the service anywhere, causing injection errors

BThe service will automatically be singleton without any configuration

CMultiple instances will be created if added to different component providers

DThe service will be tree-shaken and removed from the build

Step-by-Step Solution

Solution:

Step 1: No providedIn or module provider
Without providedIn or module-level provider, Angular does not know where to provide the service.
Step 2: Adding service to component providers creates multiple instances
If added to multiple components' providers, each gets its own instance, breaking singleton behavior.
Final Answer:
Multiple instances will be created if added to different component providers -> Option C
Quick Check:
Missing providedIn or module provider breaks singleton [OK]

Quick Trick: No providedIn or module provider means no singleton [OK]

Common Mistakes:

MISTAKES

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