Bun APIs

Overview of Bun’s native APIs available on the Bun global object and built-in modules

Bun implements a set of native APIs on the Bun global object and through several built-in modules. These APIs are heavily optimized and are the canonical “Bun-native” way to implement common functionality.

Bun strives to implement standard Web APIs wherever possible. Bun introduces new APIs primarily for server-side tasks where no standard exists, such as file I/O and starting an HTTP server. In these cases, Bun’s approach still builds atop standard APIs like Blob, URL, and Request.

server.ts

Bun.serve({
  fetch(req: Request) {
    return new Response("Success!");
  },
});

Use the links in the table to jump to the associated documentation.

Topic	APIs
HTTP Server	Bun.serve
Shell	$
Bundler	Bun.build
File I/O	Bun.file, Bun.write, Bun.stdin, Bun.stdout, Bun.stderr
Child Processes	Bun.spawn, Bun.spawnSync
TCP Sockets	Bun.listen, Bun.connect
UDP Sockets	Bun.udpSocket
WebSockets	new WebSocket() (client), Bun.serve (server)
Transpiler	Bun.Transpiler
Routing	Bun.FileSystemRouter
Streaming HTML	HTMLRewriter
Headless Browser	Bun.WebView
Hashing	Bun.password, Bun.hash, Bun.CryptoHasher, Bun.sha
CSRF Protection	Bun.CSRF.generate, Bun.CSRF.verify
SQLite	bun:sqlite
SQL Client	Bun.SQL, Bun.sql
Redis (Valkey) Client	Bun.RedisClient, Bun.redis
FFI (Foreign Function Interface)	bun:ffi
DNS	Bun.dns.lookup, Bun.dns.prefetch, Bun.dns.getCacheStats
Testing	bun:test
Workers	new Worker()
Module Loaders	Bun.plugin
Glob	Bun.Glob
Cookies	Bun.Cookie, Bun.CookieMap
Node-API	Node-API
import.meta	import.meta
Utilities	Bun.version, Bun.revision, Bun.env, Bun.main
Sleep & Timing	Bun.sleep(), Bun.sleepSync(), Bun.nanoseconds()
Random & UUID	Bun.randomUUIDv7()
System & Environment	Bun.which()
Comparison & Inspection	Bun.peek(), Bun.deepEquals(), Bun.deepMatch, Bun.inspect()
String & Text Processing	Bun.escapeHTML(), Bun.stringWidth(), Bun.indexOfLine
URL & Path Utilities	Bun.fileURLToPath(), Bun.pathToFileURL()
Compression	Bun.gzipSync(), Bun.gunzipSync(), Bun.deflateSync(), Bun.inflateSync(), Bun.zstdCompressSync(), Bun.zstdDecompressSync(), Bun.zstdCompress(), Bun.zstdDecompress()
Stream Processing	Bun.readableStreamTo*(), Bun.readableStreamToBytes(), Bun.readableStreamToBlob(), Bun.readableStreamToFormData(), Bun.readableStreamToJSON(), Bun.readableStreamToArray()
Memory & Buffer Management	Bun.ArrayBufferSink, Bun.allocUnsafe, Bun.concatArrayBuffers
Module Resolution	Bun.resolveSync()
Parsing & Formatting	Bun.semver, Bun.TOML.parse, Bun.XML, Bun.markdown, Bun.color, Bun.Image
Low-level / Internals	Bun.mmap, Bun.gc, Bun.generateHeapSnapshot, bun:jsc