Bun — JavaScript Runtime & Toolkit In-Depth Reference

Comprehensive reference for the Bun CLI (https://bun.sh/docs), covering the command reference, configuration, package manager, test runner, bundler, runtime API, shell, and module resolution. Bun is an all-in-one JavaScript runtime built on JavaScriptCore (not V8), with a native bundler, transpiler, test runner, and package manager written in Zig and C++.

Data Flow

Source file (.js/.ts/.jsx/.tsx)
  → transpiler (JS/TS/JSX → vanilla JS, dead code elimination)
    → module resolver (node_modules, exports field, tsconfig paths)
      → runtime (JavaScriptCore engine executes)
        → globals (Web API + Node.js + Bun-specific)
          → Bun API (serve, file, spawn, write, hash, etc.)

Sub-Resources

Load the reference that matches your task. When in doubt, load multiple references.

Keywords	Reference
command, subcommand, flag, bun install, bun add, bun remove, bun run, bun x, bunx, bun create, bun init, bun build, bun test, bun pm, bun upgrade, bun completions, bun link, bun unlink, bun dev, bun ci, CLI reference, --watch, --hot, --silent, --eval, --print, --preload, --inspect, --define, --loader, --env-file, --port, --smol, --no-install, --install, --bun, --filter, --workspaces, --parallel, --sequential	references/cli.md
bunfig.toml, configuration, config file, [install], [test], [run], [serve], preload, jsx, smol, logLevel, define, loader, telemetry, env, console, registry, scopes, ca, cafile, cache, lockfile, linker, globalStore, publicHoistPattern, hoistPattern, frozenLockfile, dryRun, auto, prefer, saveTextLockfile, ignoreScripts, concurrentScripts, minimumReleaseAge, security scanner, globalDir, globalBinDir, linkWorkspacePackages, noOrphans, elide-lines, shell, run.bun, run.silent	references/config.md
package manager, bun install, bun add, bun remove, bun link, bun unlink, bun pm, bun pm pack, bun pm bin, bun pm ls, bun pm whoami, bun pm cache, bun pm migrate, bun pm untrusted, bun pm trust, bun pm hash, bun pm version, bun pm pkg, bun.lock, lockfile, binary lockfile, text lockfile, trustedDependencies, backend, clonefile, hardlink, symlink, copyfile, linker, hoisted, isolated, global install, workspace, filter, omit, production, exact, yarn, frozen-lockfile, dry-run, force, no-cache, network-concurrency, concurrent-scripts, registry, scopes, ca, cafile, backend	references/package-manager.md
test runner, bun test, bun:test, test, expect, describe, beforeAll, beforeEach, afterEach, afterAll, mock, jest.fn, snapshot, toMatchSnapshot, coverage, --coverage, --timeout, --rerun-each, --retry, --concurrent, --max-concurrency, --randomize, --seed, --bail, --test-name-pattern, --reporter, --reporter-outfile, --dots, --update-snapshots, --watch, --preload, --todo, test.concurrent, test.serial, test.failing, test.todo, JUnit, CI, CLAUDECODE, AGENT, pathIgnorePatterns, coverageThreshold	references/test-runner.md
bundler, bun build, Bun.build, entrypoints, outdir, outfile, target, browser, bun, node, format, esm, cjs, iife, splitting, minify, minify-syntax, minify-whitespace, minify-identifiers, keep-names, sourcemap, linked, inline, external, external, define, drop, loader, banner, footer, naming, entry-naming, chunk-naming, asset-naming, root, publicPath, public-path, packages, no-bundle, compile, bytecode, --compile, standalone executable, windows-icon, windows-title, metafile, metafile-md, env, conditions, jsx, react-fast-refresh, react-compiler, css-chunking, optimizeImports, feature, features, BuildArtifact, BuildOutput, BuildMessage, ResolveMessage	references/bundler.md
runtime, Bun global, Bun.serve, Bun.file, Bun.write, Bun.spawn, Bun.spawnSync, Bun.hash, Bun.password, Bun.hash, Bun.CryptoHasher, Bun.Transpiler, Bun.peek, Bun.deepEquals, Bun.inspect, Bun.sleep, Bun.sleepSync, Bun.nanoseconds, Bun.which, Bun.randomUUIDv7, Bun.escapeHTML, Bun.stringWidth, Bun.stripANSI, Bun.wrapAnsi, Bun.fileURLToPath, Bun.pathToFileURL, Bun.resolveSync, Bun.gzipSync, Bun.gunzipSync, Bun.deflateSync, Bun.inflateSync, Bun.zstdCompressSync, Bun.zstdDecompressSync, Bun.readableStreamToText, Bun.readableStreamToJSON, Bun.readableStreamToArray, Bun.env, Bun.main, Bun.version, Bun.revision, Bun.Terminal, HTMLRewriter, Bun.Glob, Bun.plugin, Bun.semver, Bun.TOML, Bun.markdown, Bun.color, Bun.Image, Bun.mmap, Bun.gc, Bun.generateHeapSnapshot, Bun.ArrayBufferSink, Worker, import.meta, globals, Web API, Node.js globals, module resolution, load​er, extension order, tsconfig paths, exports field, conditions, watch mode, hot mode, --watch, --hot, auto-install	references/runtime.md
shell, Bun shell, $ template literal, $.quiet, $.text, $.json, $.lines, $.blob, $.nothrow, $.throws, $.env, $.cwd, $.braces, $.escape, redirection, pipe, command substitution, builtin commands, cd, ls, rm, echo, pwd, cat, touch, mkdir, which, mv, exit, true, false, yes, seq, dirname, basename, .sh file, shell injection, argument injection, security	references/shell.md
environment variable, BUN_PORT, PORT, BUN_INSTALL_GLOBAL_DIR, BUN_INSTALL_BIN, BUN_INSTALL_GLOBAL_STORE, BUN_FEATURE_FLAG_NO_ORPHANS, DO_NOT_TRACK, NODE_ENV, npm_token, GITHUB_TOKEN, GITHUB_API_DOMAIN, CLAUDECODE, REPL_ID, AGENT, XDG_CONFIG_HOME, env file, --env-file, .env	references/environment.md

Quick Guide

• What CLI commands does bun have? → references/cli.md
• How do I configure bun with bunfig.toml? → references/config.md
• How does the package manager work? → references/package-manager.md
• How do I run tests? → references/test-runner.md
• How do I bundle code? → references/bundler.md
• What runtime APIs does Bun provide? → references/runtime.md
• How does the Bun shell work? → references/shell.md
• What environment variables does bun use? → references/environment.md
• How do I install dependencies? → references/package-manager.md
• How do I add a dependency? → references/cli.md and references/package-manager.md
• How do I run a file or script? → references/cli.md
• How do I configure the test runner? → references/config.md and references/test-runner.md
• How do I create a standalone executable? → references/bundler.md
• How do I start an HTTP server? → references/runtime.md
• How do I read/write files? → references/runtime.md
• How do I spawn child processes? → references/runtime.md
• How do I use the Bun shell? → references/shell.md
• How do I configure auto-install? → references/config.md

Cross-Project References

• For Node.js APIs (fs, path, http, stream, crypto, util, etc.) and Node.js module system internals, see the Node.js documentation — Bun implements Node.js compatibility but this skill covers only Bun-specific behavior and differences.
• For TypeScript configuration (tsconfig.json, compilerOptions, JSX settings), see the TypeScript handbook — Bun reads tsconfig.json but this skill documents only Bun-specific configuration in bunfig.toml.
• For carapace-specific bun completion (the bun completer in completers/common/bun_completer/), see the carapace skill (in this repo).