Interfaces vs Type Aliases in TypeScript: A Comparison

Updated: January 8, 2024 By: Guest Contributor Post a comment


TypeScript, a superset of JavaScript, provides more robust typing through Interfaces and Type Aliases. Understanding their distinctions is key for type-safe code.

Understanding Interfaces

Interfaces in TypeScript are a way to describe the shape of an object. They provide a contract that an object must follow, ensuring consistent structure and typing behavior across implementations. This concept is beneficial when it comes to object-oriented programming paradigms within TypeScript.

Exploring Type Aliases

Type Aliases are similar to Interfaces in that they also describe the shape of an object, but they tend to be more flexible. Type Aliases can describe not just objects, but also primitives, union types, tuple types, and more.

Diving Deeper: When to Use Each

A comparison of practical scenarios where Interfaces outshine Type Aliases or vice versa can enlighten the decision on which to use. Interfaces are better suited for declaring object structures that must be adhered to across multiple entities. Type Aliases, on the other hand, provide a powerful way to alias complex type operations.


FeatureInterfaceType Alias
ExtensionYes, through inheritanceYes, using intersections
MergingYes, declarations merge automaticallyNo, can’t merge


FeatureInterfaceType Alias
Union TypesNoYes
Tuple TypesNoYes
Computed PropertiesNo, not directlyYes

Best Practices and Community Standards

Understanding the preferences within the TypeScript community can help make decisions on adopting Interfaces or Type Aliases. However, these standards might evolve, and being adaptable is key.

Performance Implications

One might ponder the performance implications of choosing between Interfaces and Type Aliases. However, Typescript compiles down to JavaScript, negating any real runtime performance differences. The comparison is more about developer ergonomics and maintainability.

Real World Applications

Interfaces and Type Aliases have their place in large codebases. Interfaces align well with classes and traditional object-oriented patterns. Type Aliases offer flexibility with functional programming techniques or when using advanced types.


Interfaces foster clean, maintainable code in object-oriented contexts, while Type Aliases bring versatility to type definitions. Consider both to fully leverage TypeScript’s type system.