tsc --noEmit: type check a TypeScript project without emitting files

npx tsc --noEmit runs the TypeScript type checker on the project described by tsconfig.json and writes no .js, .d.ts or source map files. It prints every type error and exits with a non-zero status when there are any, which makes it the standard type-check step in CI next to a bundler that only strips types.

Check a project

npm init -y >/dev/null
npm pkg set type=module
npm install --silent --no-audit --no-fund --save-dev typescript@7.0.2 >/dev/null 2>&1
npx tsc --init >/dev/null
mkdir src
cat > src/user.ts <<'EOF'
interface User { name: string; age: number }
export const user: User = { name: "Ada", age: "36" };
export const label = user.nmae;
EOF
npx tsc --noEmit
status=$?
ls src
exit $status

src/user.ts(2,42): error TS2322: Type 'string' is not assignable to type 'number'.
src/user.ts(3,27): error TS2339: Property 'nmae' does not exist on type 'User'.
user.ts

Both errors are reported and src/ still holds only the source file: no user.js was written. The exit status is 1 with --noEmit; a normal tsc build that finds errors still writes the output files and exits with 2.

Variants

Add it to package.json

{
  "scripts": {
    "typecheck": "tsc --noEmit"
  }
}

Then npm run typecheck runs it locally and in CI. Setting "noEmit": true in tsconfig.json has the same effect for every tsc call, which suits projects where a bundler always produces the JavaScript.

Pitfalls

• Files outside include. tsc checks only the files that include/files in tsconfig.json select (all .ts files below the folder by default). A file outside them is never checked. npx tsc --listFilesOnly shows the list.
• Passing a file name (tsc --noEmit src/a.ts) ignores tsconfig.json; TypeScript 6.0 and later stop with error TS5112 instead. See tsc file.ts and tsconfig.json.
• skipLibCheck hides errors inside dependencies' .d.ts files; that is usually wanted, but it can mask a broken type package.
• Typical errors it reports: TS2322 not assignable, TS2339 property does not exist, TS2307 cannot find module.

Confirm it worked

Introduce a deliberate type error, run the command and check that it fails, then remove the error and check that it exits 0 with no output.

FAQ