Introduction In TypeScript, you can define custom shapes using type aliases or interface. But when it comes to choosing between them, many developers ask: “TypeScript Type vs Interface?” The answer is increasingly clear: use type. type interface “TypeScript Type vs Interface?” use type While both share similarities, type offers more flexibility, supports complex patterns, and aligns better with modern TypeScript and frameworks. In this guide, you’ll learn the differences, strengths, and why type is the better default. type type What Are Types and Interfaces? Both type and interface define object shapes or function signatures: type interface // Using type
type Point = { x: number; y: number };
type SetPoint = (x: number, y: number) => void;

// Using interface
interface Point { x: number; y: number }
interface SetPoint { (x: number, y: number): void } // Using type
type Point = { x: number; y: number };
type SetPoint = (x: number, y: number) => void;

// Using interface
interface Point { x: number; y: number }
interface SetPoint { (x: number, y: number): void } They look and behave similarly here, but the differences appear in advanced use cases. Why Type Wins in Modern TypeScript But why are types preferable? 1- More Expressive type is more versatile and can describe things that interface can’t, like unions, primitives, tuples, mapped types, and conditional types. type interface // Using `type` to alias primitive types.
// `interface` cannot be used with primitives like `string`, `number`, etc.
type Name = string; 

// Using `type` to define a union type.
// `interface` does not support union types directly.
type Result = { success: true } | { error: string }; 

// Using `type` to define a tuple.
// Tuples can't be defined using `interface`; `type` is required.
type Coordinates = [number, number]; 

// Using `type` with mapped types to create a read-only version of a given type.
// This utilizes TypeScript's advanced type system, which `type` handles more flexibly than `interface`.
type Readonly<T> = { readonly [K in keyof T]: T[K] };

// Conditional type (cannot be achieved using `interface`)
type ResponseData<T extends boolean> = T extends true
  ? { success: true; data: string }
  : { success: false; error: string };

// When the flag is true, the shape has 'data'
type SuccessResponse = ResponseData<true>; // { success: true; data: string }

// When the flag is false, the shape has 'error'
type ErrorResponse = ResponseData<false>; // { success: false; error: string } // Using `type` to alias primitive types.
// `interface` cannot be used with primitives like `string`, `number`, etc.
type Name = string; 

// Using `type` to define a union type.
// `interface` does not support union types directly.
type Result = { success: true } | { error: string }; 

// Using `type` to define a tuple.
// Tuples can't be defined using `interface`; `type` is required.
type Coordinates = [number, number]; 

// Using `type` with mapped types to create a read-only version of a given type.
// This utilizes TypeScript's advanced type system, which `type` handles more flexibly than `interface`.
type Readonly<T> = { readonly [K in keyof T]: T[K] };

// Conditional type (cannot be achieved using `interface`)
type ResponseData<T extends boolean> = T extends true
  ? { success: true; data: string }
  : { success: false; error: string };

// When the flag is true, the shape has 'data'
type SuccessResponse = ResponseData<true>; // { success: true; data: string }

// When the flag is false, the shape has 'error'
type ErrorResponse = ResponseData<false>; // { success: false; error: string } Interfaces can’t express these patterns. 2- Safer and More Predictable Only interface supports declaration merging: interface interface Config { debug: boolean }
interface Config { verbose: boolean }
// Becomes: { debug: boolean; verbose: boolean } interface Config { debug: boolean }
interface Config { verbose: boolean }
// Becomes: { debug: boolean; verbose: boolean } This can be helpful in rare cases but risky in most—it leads to hard-to-debug surprises. type prevents accidental redefinitions. type 3- Works Everywhere type can extend both types and interfaces, and you can use intersection (&) for composition. type & type A = { a: string };
type B = A & { b: number };

interface I { i: boolean }
type Combined = I & { x: number }; type A = { a: string };
type B = A & { b: number };

interface I { i: boolean }
type Combined = I & { x: number }; This makes type more consistent for real-world scenarios. type 4- Ideal for Functional and React Patterns Modern frontend libraries and tools like React, Redux, and Zod tend to favor type aliases due to their flexibility, especially when working with discriminated unions, complex props, or functional patterns. React Redux Zod type discriminated unions discriminated unions // Simple React props using a type alias
type Props = { children: React.ReactNode };

// Discriminated union for Redux-like actions
type Action =
  | { type: 'start' }
  | { type: 'stop' };

// This is a discriminated union: a union of object types
// that share a common `type` field used to determine the variant. // Simple React props using a type alias
type Props = { children: React.ReactNode };

// Discriminated union for Redux-like actions
type Action =
  | { type: 'start' }
  | { type: 'stop' };

// This is a discriminated union: a union of object types
// that share a common `type` field used to determine the variant. You can’t define union types or complex props this cleanly with interface. interface When Interface Makes Sense While type is generally more flexible, interface still plays a valuable role in certain scenarios: type interface Public APIs / Libraries – interface supports declaration merging, which allows libraries to be extended or augmented safely.


OOP patterns where classes implement contracts
interface IUser { 
id: string; 
login(): void; 
}

class Admin implements IUser { 
id = 'admin'; 
login() {} 
} Public APIs / Libraries – interface supports declaration merging, which allows libraries to be extended or augmented safely. Public APIs / Libraries – interface supports declaration merging, which allows libraries to be extended or augmented safely. Public APIs / Libraries interface declaration merging OOP patterns where classes implement contracts
interface IUser { 
id: string; 
login(): void; 
}

class Admin implements IUser { 
id = 'admin'; 
login() {} 
} OOP patterns where classes implement contracts OOP patterns interface IUser { 
id: string; 
login(): void; 
}

class Admin implements IUser { 
id = 'admin'; 
login() {} 
} interface IUser { 
id: string; 
login(): void; 
}

class Admin implements IUser { 
id = 'admin'; 
login() {} 
} But even here, you can use type instead. type type IUser = {
  id: string;
  login(): void;
}

class Admin implements IUser {
  id = 'admin';
  login() {}
} type IUser = {
  id: string;
  login(): void;
}

class Admin implements IUser {
  id = 'admin';
  login() {}
} While both versions work, interface tends to be preferred in OOP-heavy codebases for its semantic clarity and support for extension via extends or declaration merging. interface extends Conclusion In most real-world TypeScript codebases, type outshines interface. It handles everything from unions to tuples, supports mapped and conditional types, and avoids unexpected behaviors like declaration merging. type interface At the end of the day, unless you’re exposing a public OOP-style API or need declaration merging, stick with type. type Think Of It If you enjoyed this article, I’d truly appreciate it if you could share it—it really motivates me to keep creating more helpful content! If you’re interested in exploring more, check out these articles. 4 Ways To Handle Asynchronous JavaScript
Overloading vs Overriding in TypeScript
How to Use as const in TypeScript Effectively 4 Ways To Handle Asynchronous JavaScript 4 Ways To Handle Asynchronous JavaScript 4 Ways To Handle Asynchronous JavaScript Overloading vs Overriding in TypeScript Overloading vs Overriding in TypeScript Overloading vs Overriding in TypeScript How to Use as const in TypeScript Effectively How to Use as const in TypeScript Effectively How to Use as const in TypeScript Effectively And to learn more, please check the TypeScript Documentation: TypeScript Documentation Thanks for sticking with me until the end—I hope you found this article valuable and enjoyable!

The code in this story is for educational purposes. The readers are solely responsible for whatever they build with it.

Public

Breaking From ForEach in JavaScript

If you found my content helpful, check out my blog for more

Read My Stories

Too Long; Didn't Read

Make resilience your competitive advantage

TypeScript Showdown: Type vs Interface — Why 'Type' Wins

About Author

Comments

TOPICS

THIS ARTICLE WAS FEATURED IN

Related Stories

Untitled Story

Breaking From ForEach in JavaScript

104 Stories To Learn About Go

105 Stories To Learn About Functional Programming

100+ Free Pluralsight Courses to learn Python, Java, and Spring Boot

10 Websites to Learn JavaScript for Beginners

Breaking From ForEach in JavaScript

104 Stories To Learn About Go

105 Stories To Learn About Functional Programming

100+ Free Pluralsight Courses to learn Python, Java, and Spring Boot

10 Websites to Learn JavaScript for Beginners

Light-Mode

Classic

Newspaper

Dark-Mode

Neon Noir

Minty

HN StartUps