bun build ./index.ts --outdir ./out: bundle with Bun

bun build ./index.ts --outdir ./out bundles the entry file and everything it imports into out/index.js, stripping TypeScript types and resolving node_modules. The default target is the browser; add --target bun or --target node for server code, --minify for production, and --compile to produce a single native executable that includes the Bun runtime.

Example

cat > greet.ts <<'EOF'
export const greet = (name: string): string => `hello ${name}`;
EOF
cat > index.ts <<'EOF'
import { greet } from "./greet";
console.log(greet("bun"));
EOF
npx --yes bun@1 build ./index.ts --outdir ./out > /dev/null 2>&1
echo "--- out/index.js"
cat out/index.js
npx --yes bun@1 build ./index.ts --outdir ./min --minify > /dev/null 2>&1
echo "--- min/index.js"
cat min/index.js
echo
node out/index.js

--- out/index.js
// greet.ts
var greet = (name) => `hello ${name}`;

// index.ts
console.log(greet("bun"));
--- min/index.js
var o=(e)=>`hello ${e}`;console.log(o("bun"));

hello bun

Both modules end up in one file, and the type annotations are gone, so the output runs in Node.js or a browser.

Types are stripped, not checked

cat > bad.ts <<'EOF'
const n: number = "not a number";
console.log(n);
EOF
npx --yes bun@1 build ./bad.ts --outfile bad.js --target node > /dev/null 2>&1
echo "build exit=$?"
cat bad.js

build exit=0
// bad.ts
var n = "not a number";
console.log(n);

The build succeeds although the code assigns a string to a number. Like esbuild and other fast bundlers, Bun transpiles TypeScript without running the type checker. Add --check to type-check the entry points and everything they import (nothing is bundled if there are type errors), or keep tsc --noEmit as a separate CI step.

Main options

Choosing a target

A server bundle built with the default browser target can pick up browser builds of dependencies or fail at run time on Node.js APIs, so set the target explicitly for anything that does not run in a browser.

Standalone executable

bun build ./cli.ts --compile --outfile mycli
./mycli

The executable embeds the Bun runtime, so it is tens of megabytes and runs on machines without Bun. Use --target=bun-linux-x64, bun-darwin-arm64 or bun-windows-x64 to cross-compile for another platform.

FAQ