typescript-interface-vs-type

Installation
SKILL.md

TypeScript: Interface vs Type

Core Principle

Use interface until you need features from type.

This is the official TypeScript recommendation from the TypeScript Handbook.

When to Use Interface

Use interface for:

  • Object type definitions
  • Extending other object types
  • Class implementations
  • Declaration merging (augmenting existing types)

When to Use Type

Use type only when you need:

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Jan 30, 2026