Understanding when to use TypeScript instead of JavaScript can help you make the right decision for your project. Several criteria can guide your choice.

• Consider project size: TypeScript shines in medium to large codebases where the complexity of the application makes bugs harder to track down;
• Think about team collaboration. If you are working with multiple developers, TypeScript's type system makes it easier to understand each other's code, reducing miscommunication and onboarding time;
• Codebase longevity is important. Projects expected to grow and be maintained over several years benefit from TypeScript because its types make refactoring safer and future changes less risky.

Its static type checking can prevent many common errors before code even runs.

You should also consider the nature of your project before deciding to use TypeScript. Complex applications—such as enterprise web apps, large-scale APIs, and long-term maintained products—are ideal candidates for TypeScript. For example, a business dashboard with dozens of contributors, or a shared code library used by multiple teams, can benefit from the clarity and safety TypeScript provides. On the other hand, small scripts, quick prototypes, or one-off tools may not need the overhead of TypeScript. If your project is a simple web page or a short-lived proof-of-concept, JavaScript may be a better fit due to its lower setup requirements and faster iteration.