Interface vs Type Alias: Which one should you use?

One of the most common questions in TypeScript is when to use an Interface and when to use a Type alias. Generally, interfaces are better for defining object shapes that can be extended via declaration merging, while types are more flexible for unions, intersections, and primitives. However, with recent versions of TypeScript, the functional differences have become minimal, so it often comes down to personal or team preference.

All 3 comments

Zeeshan Saleem

I used to prefer Interfaces for everything because of the better error messages in older TypeScript versions. But now that Types can do almost everything (like implements and extends), I find myself using Types more often just for consistency with unions.

Zeeshan Saleem

That's a good point. I still stick to Interfaces for defining public API shapes for libraries, though. Declaration merging is a lifesaver when you need to extend a third-party library's definition without forking it.

Sheraz Ahmad

Good Explanation