node app.ts: run a TypeScript file directly with Node.js

node app.ts runs a TypeScript file directly on Node.js 22.18 or later and 23.6 or later: Node.js strips the type annotations and executes the remaining JavaScript, with no build step, no ts-node and no tsx. It does not type-check, and it supports only TypeScript syntax that can be erased without generating code. Earlier 22.x releases (from 22.6) need the --experimental-strip-types flag.

Run a file with imports

cat > util.ts <<'EOF'
export interface User { name: string }
export const greet = (u: User): string => `hello ${u.name}`;
EOF
cat > app.ts <<'EOF'
import { greet, type User } from './util.ts';
const user: User = { name: 'Ada' };
console.log(greet(user));
EOF
node app.ts

hello Ada

Two rules make this work. Relative imports keep the real .ts extension (./util.ts, not ./util), because Node.js resolves files exactly as written. Type-only imports use import type or the inline type keyword, so the import can be dropped completely when the types are removed. The TypeScript options verbatimModuleSyntax, allowImportingTsExtensions and erasableSyntaxOnly make your editor enforce the same rules.

Types are removed, not checked

cat > bad.ts <<'EOF'
const port: number = "8080";
console.log(port, typeof port);
EOF
node bad.ts

8080 string

The annotation disappears at run time, so the value keeps the type it really has. Run npx tsc --noEmit to see the type error (TS2322).

Syntax that needs a transform

cat > color.ts <<'EOF'
enum Color { Red, Green }
console.log(Color.Green);
EOF
node color.ts 2>&1 | grep -E "^SyntaxError"
echo "--- with --experimental-transform-types"
node --experimental-transform-types color.ts 2>&1 | grep -v -E "ExperimentalWarning|trace-warnings"

SyntaxError [ERR_UNSUPPORTED_TYPESCRIPT_SYNTAX]: TypeScript enum is not supported in strip-only mode
--- with --experimental-transform-types
1

Module format

A .ts file follows the same rules as a .js file: it is an ES module when the nearest package.json has "type": "module", or when Node.js detects import/export syntax; .mts is always ESM and .cts always CommonJS. Mixing require and import in one file gives the same errors as in JavaScript, such as Cannot use import statement outside a module.

How to confirm it works

Run node --version: 22.18.0 or later (or 23.6.0 or later) strips types by default. On 22.6 to 22.17 add --experimental-strip-types; on 20.x and older the .ts extension is unknown and the file fails with ERR_UNKNOWN_FILE_EXTENSION. node --no-experimental-strip-types app.ts turns the feature off, which shows whether type stripping is what runs your file.

FAQ