Single-file executable

Bun's bundler implements a --compile flag for generating a standalone binary from a TypeScript or JavaScript file.

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

console.log("Hello world!");

This bundles cli.ts into an executable that can be executed directly:

$ ./mycli
Hello world!

All imported files and packages are bundled into the executable, along with a copy of the Bun runtime. All built-in Bun and Node.js APIs are supported.

Cross-compile to other platforms

The --target flag lets you compile your standalone executable for a different operating system, architecture, or version of Bun than the machine you're running bun build on.

To build for Linux x64 (most servers):

bun build --compile --target=bun-linux-x64 ./index.ts --outfile myapp

# To support CPUs from before 2013, use the baseline version (nehalem)
bun build --compile --target=bun-linux-x64-baseline ./index.ts --outfile myapp

# To explicitly only support CPUs from 2013 and later, use the modern version (haswell)
# modern is faster, but baseline is more compatible.
bun build --compile --target=bun-linux-x64-modern ./index.ts --outfile myapp

To build for Linux ARM64 (e.g. Graviton or Raspberry Pi):

# Note: the default architecture is x64 if no architecture is specified.
bun build --compile --target=bun-linux-arm64 ./index.ts --outfile myapp

To build for Windows x64:

bun build --compile --target=bun-windows-x64 ./path/to/my/app.ts --outfile myapp

# To support CPUs from before 2013, use the baseline version (nehalem)
bun build --compile --target=bun-windows-x64-baseline ./path/to/my/app.ts --outfile myapp

# To explicitly only support CPUs from 2013 and later, use the modern version (haswell)
bun build --compile --target=bun-windows-x64-modern ./path/to/my/app.ts --outfile myapp

# note: if no .exe extension is provided, Bun will automatically add it for Windows executables

To build for macOS arm64:

bun build --compile --target=bun-darwin-arm64 ./path/to/my/app.ts --outfile myapp

To build for macOS x64:

bun build --compile --target=bun-darwin-x64 ./path/to/my/app.ts --outfile myapp

Supported targets

The order of the --target flag does not matter, as long as they're delimited by a -.

On x64 platforms, Bun uses SIMD optimizations which require a modern CPU supporting AVX2 instructions. The -baseline build of Bun is for older CPUs that don't support these optimizations. Normally, when you install Bun we automatically detect which version to use but this can be harder to do when cross-compiling since you might not know the target CPU. You usually don't need to worry about it on Darwin x64, but it is relevant for Windows x64 and Linux x64. If you or your users see "Illegal instruction" errors, you might need to use the baseline version.

Deploying to production

Compiled executables reduce memory usage and improve Bun's start time.

Normally, Bun reads and transpiles JavaScript and TypeScript files on import and require. This is part of what makes so much of Bun "just work", but it's not free. It costs time and memory to read files from disk, resolve file paths, parse, transpile, and print source code.

With compiled executables, you can move that cost from runtime to build-time.

When deploying to production, we recommend the following:

bun build --compile --minify --sourcemap ./path/to/my/app.ts --outfile myapp

Bytecode compilation

To improve startup time, enable bytecode compilation:

bun build --compile --minify --sourcemap --bytecode ./path/to/my/app.ts --outfile myapp

Using bytecode compilation, tsc starts 2x faster:

Bytecode compilation moves parsing overhead for large input files from runtime to bundle time. Your app starts faster, in exchange for making the bun build command a little slower. It doesn't obscure source code.

Experimental: Bytecode compilation is an experimental feature introduced in Bun v1.1.30. Only cjs format is supported (which means no top-level-await). Let us know if you run into any issues!

What do these flags do?

The --minify argument optimizes the size of the transpiled output code. If you have a large application, this can save megabytes of space. For smaller applications, it might still improve start time a little.

The --sourcemap argument embeds a sourcemap compressed with zstd, so that errors & stacktraces point to their original locations instead of the transpiled location. Bun will automatically decompress & resolve the sourcemap when an error occurs.

The --bytecode argument enables bytecode compilation. Every time you run JavaScript code in Bun, JavaScriptCore (the engine) will compile your source code into bytecode. We can move this parsing work from runtime to bundle time, saving you startup time.

Worker

To use workers in a standalone executable, add the worker's entrypoint to the CLI arguments:

bun build --compile ./index.ts ./my-worker.ts --outfile myapp

Then, reference the worker in your code:

console.log("Hello from Bun!");

// Any of these will work:
new Worker("./my-worker.ts");
new Worker(new URL("./my-worker.ts", import.meta.url));
new Worker(new URL("./my-worker.ts", import.meta.url).href);

As of Bun v1.1.25, when you add multiple entrypoints to a standalone executable, they will be bundled separately into the executable.

In the future, we may automatically detect usages of statically-known paths in new Worker(path) and then bundle those into the executable, but for now, you'll need to add it to the shell command manually like the above example.

If you use a relative path to a file not included in the standalone executable, it will attempt to load that path from disk relative to the current working directory of the process (and then error if it doesn't exist).

SQLite

You can use bun:sqlite imports with bun build --compile.

By default, the database is resolved relative to the current working directory of the process.

import db from "./my.db" with { type: "sqlite" };

console.log(db.query("select * from users LIMIT 1").get());

That means if the executable is located at /usr/bin/hello, the user's terminal is located at /home/me/Desktop, it will look for /home/me/Desktop/my.db.

$ cd /home/me/Desktop
$ ./hello

Embed assets & files

Standalone executables support embedding files.

To embed files into an executable with bun build --compile, import the file in your code

// this becomes an internal file path
import icon from "./icon.png" with { type: "file" };
import { file } from "bun";

export default {
  fetch(req) {
    // Embedded files can be streamed from Response objects
    return new Response(file(icon));
  },
};

Embedded files can be read using Bun.file's functions or the Node.js fs.readFile function (in "node:fs").

For example, to read the contents of the embedded file:

import icon from "./icon.png" with { type: "file" };
import { file } from "bun";

const bytes = await file(icon).arrayBuffer();

Embed SQLite databases

If your application wants to embed a SQLite database, set type: "sqlite" in the import attribute and the embed attribute to "true".

import myEmbeddedDb from "./my.db" with { type: "sqlite", embed: "true" };

console.log(myEmbeddedDb.query("select * from users LIMIT 1").get());

This database is read-write, but all changes are lost when the executable exits (since it's stored in memory).

Embed N-API Addons

As of Bun v1.0.23, you can embed .node files into executables.

const addon = require("./addon.node");

console.log(addon.hello());

Unfortunately, if you're using @mapbox/node-pre-gyp or other similar tools, you'll need to make sure the .node file is directly required or it won't bundle correctly.

Embed directories

To embed a directory with bun build --compile, use a shell glob in your bun build command:

bun build --compile ./index.ts ./public/**/*.png

Then, you can reference the files in your code:

import icon from "./public/assets/icon.png" with { type: "file" };
import { file } from "bun";

export default {
  fetch(req) {
    // Embedded files can be streamed from Response objects
    return new Response(file(icon));
  },
};

This is honestly a workaround, and we expect to improve this in the future with a more direct API.

Listing embedded files

To get a list of all embedded files, use Bun.embeddedFiles:

import "./icon.png" with { type: "file" };
import { embeddedFiles } from "bun";

console.log(embeddedFiles[0].name); // `icon-${hash}.png`

Bun.embeddedFiles returns an array of Blob objects which you can use to get the size, contents, and other properties of the files.

embeddedFiles: Blob[]

The list of embedded files excludes bundled source code like .ts and .js files.

Content hash

By default, embedded files have a content hash appended to their name. This is useful for situations where you want to serve the file from a URL or CDN and have fewer cache invalidation issues. But sometimes, this is unexpected and you might want the original name instead:

To disable the content hash, pass --asset-naming to bun build --compile like this:

bun build --compile --asset-naming="[name].[ext]" ./index.ts

Minification

To trim down the size of the executable a little, pass --minify to bun build --compile. This uses Bun's minifier to reduce the code size. Overall though, Bun's binary is still way too big and we need to make it smaller.

Unsupported CLI arguments

Currently, the --compile flag can only accept a single entrypoint at a time and does not support the following flags:

• --outdir — use outfile instead.
• --splitting
• --public-path
• --target=node or --target=browser
• --format - always outputs a binary executable. Internally, it's almost esm.
• --no-bundle - we always bundle everything into the executable.