Difference between Type and Interface in Typescript.

🚀 “What’s the difference between type and interface in TypeScript?” — The Most Asked Interview Question!

Last week during a technical interview, the interviewer smiled and asked me one of the classic TypeScript questions:

👉 “Can you tell me the difference between type and interface?”

I’ve been asked this so many times that I finally decided to put the answer here for everyone who is preparing for React / React Native / TypeScript interviews.

🟦 My simple, interview-friendly answer:

1️⃣ interface is mainly for objects

It’s TypeScript’s way of defining the shape of an object. And yes — interfaces can be extended easily.

interface User {
  name: string;
  age: number;
}

interface Employee extends User {
  salary: number;
}
        

2️⃣ type is more flexible

It can represent unions, primitives, tuples, functions, etc.

type Status = "success" | "error";
type Point = [number, number];
type UserFn = () => void;
        

🟩 3️⃣ Both can describe objects — that’s where confusion begins

type User = { name: string }
interface User { name: string }
        

Both work. But their abilities differ 👇

🟧 4️⃣ Interfaces can merge, types cannot

If you declare an interface twice, TypeScript merges them automatically:

interface User { name: string }
interface User { age: number }

// becomes:
interface User { name: string; age: number }
        

❌ Doing this with type gives an error.

🟪 5️⃣ Types support unions & intersections

This is something interfaces cannot do:

type ApiResponse = SuccessResponse | ErrorResponse;
        

🎯 My closing line in the interview:

“Use interface when modelling objects and extending shapes. Use type when you need flexibility like unions, tuples, or combining multiple types.”

Interviewer nodded. ✔️ Interview continued smoothly. 😄

💬 What about you?

Have you been asked this question too? How do you answer it?