What is CommonModule in Angular, and when do you need to import it?

Answer: CommonModule provides common directives like *ngIf, *ngFor, ngClass, etc. You import it in feature modules or any module other than the root module. Don’t import BrowserModule in feature modules; instead, import CommonModule there.

What interviewers expect

• A clear definition tied to Angular in Angular projects
• Trade-offs (performance, maintainability, security, cost)
• When you would and would not use it in production

Real-world example

In a production Angular application, teams apply this when handling user-facing features or integration boundaries. For example, you might use it during a sprint where reliability and observability matter—logging metrics, validating edge cases, and documenting the decision in an ADR so future developers understand why the approach was chosen.

How to explain in the interview

1. Define the concept in one or two sentences.
2. Context — where it fits in Angular architecture.
3. Example — a specific project, bug, or performance win.
4. Trade-off — what you gain vs what you sacrifice.

Tip: Practice aloud on Toolliyo mock interview or the Interview Q&A section before your real interview.