TypeScript Online Compiler | Free Online Compiler

Code

type User = {
    name: string;
    points: number;
};

const users: User[] = [
    { name: "Asha", points: 12 },
    { name: "Noah", points: 8 }
];

const total = users.reduce((sum, user) => sum + user.points, 0);
console.log("Total points:", total);

STDIN (optional)

Args (space separated)

Output

What Is the TypeScript Online Compiler?

This tool lets you compile and run TypeScript code directly in your browser without installing anything locally. It is powered by the Piston execution engine, which compiles your TypeScript source and executes the resulting JavaScript in a sandboxed environment. Whether you are exploring type annotations, building interfaces, or experimenting with generics, this compiler provides instant feedback on your code.

TypeScript extends JavaScript with a static type system that catches errors at compile time rather than at runtime. This online compiler gives you full access to those type-checking capabilities, including interfaces, type aliases, union types, intersection types, enums, and generics. You can write modern TypeScript syntax and see the compiled output immediately in the Output panel.

How It Works

Write your TypeScript code in the editor panel. The editor starts with a sample program that demonstrates type aliases and array methods, but you can replace it with any valid TypeScript code.
Provide input in the STDIN field if your program reads from standard input. Each line in the STDIN box corresponds to one line of input available to your program. Leave this field empty if your program does not require any input.
Add command-line arguments in the Args field if your script reads from process.argv. Enter arguments separated by spaces, just as you would in a terminal.
Click the Run button to send your code to the Piston execution server. The server first compiles your TypeScript to JavaScript using the TypeScript compiler, then executes the resulting JavaScript and captures all output.
View the results in the Output panel. You will see everything your program logs to the console, along with any compilation errors or runtime exceptions if something goes wrong.

Step-by-Step Example

Suppose you want to define an interface for a product, create a typed array, and compute a total using array methods. Here is how you would do it:

First, type the following code into the editor panel:

interface Product {
    name: string;
    price: number;
}

const products: Product[] = [
    { name: "Notebook", price: 12.99 },
    { name: "Pen", price: 1.49 },
    { name: "Eraser", price: 0.79 }
];

const total = products.reduce((sum, p) => sum + p.price, 0);
const names = products.map(p => p.name.toUpperCase());

console.log("Products:", names.join(", "));
console.log("Total:", total.toFixed(2));

Now click the Run button. The compiler sends your TypeScript to the execution server, which compiles it to JavaScript and runs it. After a moment, the Output panel displays:

Products: NOTEBOOK, PEN, ERASER
Total: 15.27

The interface ensures that every object in the array has the correct shape. The reduce method computes the total price, and map transforms each product name to uppercase. If you misspell a property or use the wrong type, the TypeScript compiler catches the error before execution.

Use Cases

Learning TypeScript fundamentals. Beginners can experiment with type annotations, interfaces, enums, and generics in a zero-setup environment and see compiler feedback instantly.
Testing type system features. Try out advanced patterns like conditional types, mapped types, template literal types, and utility types without setting up a local project.
Converting JavaScript to TypeScript. Paste existing JavaScript code, add type annotations incrementally, and verify that the compiler accepts your changes before updating your real project.
Preparing for coding interviews. Many interviews involve writing typed functions or solving algorithmic problems. Use this compiler to practice with TypeScript and validate your solutions with real execution.
Running quick type experiments. When you need to verify how a particular TypeScript feature works, such as type narrowing, discriminated unions, or generic constraints, this compiler gives you an answer in seconds.

Limitations and Notes

Single-file execution only. The compiler runs a single TypeScript file (main.ts). Multi-file projects with imports across files are not supported.
No node_modules or npm packages. You cannot install or import third-party packages. Only TypeScript built-in types and standard JavaScript APIs are available.
No tsconfig.json configuration. The compiler uses default TypeScript settings. You cannot customize compiler options like strict mode, target, or module resolution.
Standard library types are available. You can use built-in types such as Array, Map, Set, Promise, and other standard JavaScript and TypeScript types.
Execution timeout applies. Programs that run for too long or enter infinite loops are terminated automatically to protect server resources.
No DOM types. Browser-specific types like document, window, and HTMLElement are not available since code runs in a server-side Node.js environment.

Frequently Asked Questions

What TypeScript version does this compiler use?

It uses the latest available TypeScript version provided by the Piston execution engine.

Can I use interfaces and type aliases?

Yes, the full TypeScript type system is supported, including interfaces, type aliases, union types, and intersection types.

Can I import npm packages?

No, only TypeScript built-in types and standard library features are available. Third-party npm packages cannot be installed.

Is there a tsconfig.json?

No, the compiler uses default TypeScript compiler settings. You cannot provide a custom tsconfig.json.

Does this support enums and generics?

Yes, enums, generics, mapped types, conditional types, and other advanced TypeScript features are fully supported.

Can I use async/await?

Yes, modern JavaScript and TypeScript syntax including async/await, Promises, and other ES2015+ features are supported.

Is strictNullChecks enabled?

Default TypeScript compiler settings apply. You cannot customize compiler flags in this environment.

Can I use decorators?

Decorator support depends on the runtime TypeScript version. Decorators are an experimental feature and may or may not be enabled by default.

TypeScript Compiler