Node built-ins

Built-ins import with or without the node: prefix. Labels are explained on the overview.

Module	Status	Notes
assert, assert/strict	🟡 Partial	Common assertions (strictEqual, deepStrictEqual, rejects, …).
async_hooks	🟡 Partial	AsyncLocalStorage keeps its store only synchronously; it’s lost across await and timers. createHook does nothing.
buffer	✅ Works	Includes Blob, File, atob, btoa, isUtf8, isAscii.
child_process	⚪ Stub	No processes in the browser.
cluster	⚪ Stub	isPrimary is true; fork throws.
console	🟡 Partial	The global console. No Console class.
constants	⚪ Stub	Empty object.
crypto	🟡 Partial	createHash/createHmac (md5, ripemd160, sha1, sha2, sha3, blake2), hash, pbkdf2, scrypt (sync and callback), randomBytes, randomUUID, randomInt, getRandomValues, timingSafeEqual, webcrypto/subtle. No ciphers, sign/verify, KeyObject, generateKey*.
dgram	❌ Missing
diagnostics_channel	⚪ Stub	Subscribers never receive messages.
dns, dns/promises	🟡 Partial	lookup resolves only localhost.
domain	❌ Missing
events	✅ Works	EventEmitter, once, on, with AbortSignal.
fs, fs/promises	🟡 Partial	Sync, callback and promise APIs over the project’s files: read/write/append, stat, readdir (with Dirent), mkdir, rm, rename, copyFile, cp, file descriptors, FileHandle, read/write streams. watch (also recursive) and watchFile fire on changes. No symlinks or hard links; chmod/chown do nothing; fs/promises watch never yields.
http	🟡 Partial	createServer().listen() serves the preview: streamed responses, cookies, WebSocket upgrade. http.request/http.get throw; use fetch.
https	🟡 Partial	Like http; no TLS.
http2	⚪ Stub
inspector	⚪ Stub
module	🟡 Partial	builtinModules, isBuiltin. createRequire serves built-ins; package requires in ES modules work for string literals (see Toolchain).
net	⚪ Stub	isIP* works; no sockets.
os	🟡 Partial	Fixed values: Linux, x64, /home/user, /tmp. cpus() and networkInterfaces() are empty.
path, path/posix	✅ Works	POSIX only. path.win32 behaves like POSIX; path/win32 is missing.
perf_hooks	🟡 Partial	performance, PerformanceObserver. monitorEventLoopDelay reports zeros.
process	🟡 Partial	Reports Linux x64 and Node v24.3.0. env, cwd, chdir, nextTick, hrtime, memoryUsage, uptime. stdout/stderr go to the console. argv is ["bun", entry]; stdin never emits; exit and kill throw.
punycode	✅ Works
querystring	✅ Works
readline, readline/promises	⚪ Stub
repl	❌ Missing
sqlite	❌ Missing	Use bun:sqlite.
stream, stream/promises	✅ Works	Based on readable-stream. Readable.toWeb/fromWeb are basic.
stream/web	✅ Works	The browser’s web stream classes.
string_decoder	✅ Works
sys	🟡 Partial	Same as util.
test	❌ Missing	Use bun:test.
timers, timers/promises	✅ Works	ref, unref, refresh, promise timers with AbortSignal.
tls	⚪ Stub
trace_events	❌ Missing
tty	🟡 Partial	isatty returns false.
url	✅ Works	URL, URLSearchParams, fileURLToPath, pathToFileURL, parse.
util, util/types	🟡 Partial	format, inspect, promisify, callbackify, inherits, deprecate, types, isDeepStrictEqual, parseEnv, styleText (no colors). No parseArgs, MIMEType; debuglog does nothing.
v8	⚪ Stub
vm	⚪ Stub
wasi	❌ Missing
worker_threads	🟡 Partial	isMainThread, MessageChannel, BroadcastChannel. new Worker() throws.
zlib	⚪ Stub	All functions throw. Web CompressionStream works.