Runtime Standards & Compatibility

Node.js Compatibility

Bun's compatibility status with Node.js APIs, modules, and globals

Every day, Bun gets closer to 100% Node.js API compatibility. Popular frameworks like Next.js, Express, and millions of npm packages intended for Node.js work with Bun. To ensure compatibility, we run thousands of tests from Node.js' test suite before every release of Bun.

If a package works in Node.js but doesn't work in Bun, we consider it a bug in Bun. Open an issue and we'll fix it.

This page is updated regularly and reflects the latest version of Bun's compatibility with Node.js v23.

Built-in Node.js modules

`node:assert`

🟢 Fully implemented.

`node:buffer`

🟢 Fully implemented.

`node:console`

🟢 Fully implemented.

`node:dgram`

🟢 Fully implemented. > 90% of Node.js's test suite passes.

`node:diagnostics_channel`

🟢 Fully implemented.

`node:dns`

🟢 Fully implemented. > 90% of Node.js's test suite passes.

`node:events`

🟢 Fully implemented. 100% of Node.js's test suite passes. EventEmitterAsyncResource uses AsyncResource underneath.

`node:fs`

🟢 Fully implemented. 92% of Node.js's test suite passes.

`node:http`

🟢 Fully implemented. The outgoing client request body is buffered instead of streamed.

`node:https`

🟢 APIs are implemented, but Agent is not always used.

`node:os`

🟢 Fully implemented. 100% of Node.js's test suite passes.

`node:path`

🟢 Fully implemented. 100% of Node.js's test suite passes.

`node:punycode`

🟢 Fully implemented. 100% of Node.js's test suite passes, deprecated by Node.js.

`node:querystring`

🟢 Fully implemented. 100% of Node.js's test suite passes.

`node:readline`

🟢 Fully implemented.

`node:stream`

🟢 Fully implemented.

`node:string_decoder`

🟢 Fully implemented. 100% of Node.js's test suite passes.

`node:timers`

🟢 Use the global setTimeout and related functions instead.

`node:tty`

🟢 Fully implemented.

`node:url`

🟢 Fully implemented.

`node:zlib`

🟢 Fully implemented. 98% of Node.js's test suite passes.

`node:async_hooks`

🟡 AsyncLocalStorage and AsyncResource are implemented. v8 promise hooks are not called, and its usage is strongly discouraged.

`node:child_process`

🟡 Missing proc.gid proc.uid. Stream class not exported. IPC cannot send socket handles. Node.js ↔ Bun IPC can be used with JSON serialization.

`node:cluster`

🟡 Handles and file descriptors cannot be passed between workers, so load-balancing HTTP requests across processes is only supported on Linux (through SO_REUSEPORT). Otherwise, implemented but not battle-tested.

`node:crypto`

🟡 Missing secureHeapUsed setEngine setFips

`node:domain`

🟡 Missing Domain active

`node:http2`

🟡 Client & server are implemented (95.25% of gRPC's test suite passes).

`node:module`

🟡 Missing syncBuiltinESMExports, Module#load(). Overriding require.cache is supported for ESM & CJS modules. module._extensions, module._pathCache, module._cache are no-ops. module.register is not implemented; we recommend Bun.plugin instead.

`node:net`

🟢 Fully implemented.

`node:perf_hooks`

🟡 APIs are implemented, but the Node.js test suite for this module does not pass.

`node:process`

🟡 See process Global.

`node:sys`

🟡 See node:util.

`node:tls`

🟡 Missing tls.createSecurePair.

`node:util`

🟡 Missing getCallSite getCallSites getSystemErrorMap getSystemErrorMessage transferableAbortSignal transferableAbortController

`node:v8`

🟡 writeHeapSnapshot and getHeapSnapshot are implemented. serialize and deserialize use JavaScriptCore's wire format instead of V8's. Other methods are not implemented. For profiling, use bun:jsc instead.

`node:vm`

🟡 Core functionality and ES modules are implemented, including vm.Script, vm.createContext, vm.runInContext, vm.runInNewContext, vm.runInThisContext, vm.compileFunction, vm.isContext, vm.Module, vm.SourceTextModule, vm.SyntheticModule, and importModuleDynamically support. Options like timeout and breakOnSigint are fully supported.

`node:wasi`

🟡 Partially implemented.

`node:worker_threads`

🟡 Worker doesn't support the following options: stdin stdout stderr trackedUnmanagedFds resourceLimits. Missing markAsUntransferable moveMessagePortToContext.

`node:inspector`

🟡 Partially implemented. The Profiler API is supported (Profiler.enable, Profiler.disable, Profiler.start, Profiler.stop, Profiler.setSamplingInterval). Other inspector APIs are not implemented.

`node:repl`

🟡 Mostly implemented. bun --interactive starts a Node.js-compatible REPL. Result previews (which need V8's inspector-based side-effect-free eval), tab-completion of let/const/class bindings in useGlobal: true mode, and some V8-specific error-message wording differ.

`node:sqlite`

🟢 Fully implemented. backup() runs synchronously and blocks the event loop for the duration of the copy (Node runs it on a worker thread). A Buffer/Uint8Array database path must be valid UTF-8 (Node passes the raw bytes through; Bun rejects non-UTF-8 with ERR_INVALID_ARG_VALUE). On macOS, Bun uses the system libsqlite3.dylib; loadExtension() (and, on older macOS releases, createSession()/applyChangeset()) require a full SQLite build — call require("bun:sqlite").Database.setCustomSQLite(path) before opening a database.

`node:test`

🟡 Partially implemented. The in-process API works when test files run under bun test: tests, suites, subtests, hooks, t.plan(), t.assert, assert.register(), t.waitFor(), getTestContext(), and t.mock (function/method/getter/setter/property mocks and mock timers). Missing run(), node:test/reporters, snapshot testing, mock.module(), code coverage, --test-only, test-level signal/t.signal abort, and Node's --test CLI runner mode. test.only() / {only: true} are accepted but do not filter. concurrency is validated but subtests always run serially. Use bun:test instead.

`node:trace_events`

🟢 Fully implemented.

Node.js globals

The following list covers every global implemented by Node.js and Bun's compatibility status for each.

`AbortController`

🟢 Fully implemented.

`AbortSignal`

🟢 Fully implemented.

`Blob`

🟢 Fully implemented.

`Buffer`

🟢 Fully implemented.

`ByteLengthQueuingStrategy`

🟢 Fully implemented.

`__dirname`

🟢 Fully implemented.

`__filename`

🟢 Fully implemented.

`atob()`

🟢 Fully implemented.

`Atomics`

🟢 Fully implemented.

`BroadcastChannel`

🟢 Fully implemented.

`btoa()`

🟢 Fully implemented.

`clearImmediate()`

🟢 Fully implemented.

`clearInterval()`

🟢 Fully implemented.

`clearTimeout()`

🟢 Fully implemented.

`CompressionStream`

🟢 Fully implemented.

`console`

🟢 Fully implemented.

`CountQueuingStrategy`

🟢 Fully implemented.

`Crypto`

🟢 Fully implemented.

`SubtleCrypto (crypto)`

🟢 Fully implemented.

`CryptoKey`

🟢 Fully implemented.

`CustomEvent`

🟢 Fully implemented.

`DecompressionStream`

🟢 Fully implemented.

`Event`

🟢 Fully implemented.

`EventTarget`

🟢 Fully implemented.

`exports`

🟢 Fully implemented.

`fetch`

🟢 Fully implemented.

`FormData`

🟢 Fully implemented.

`global`

🟢 Implemented. global is an object containing all objects in the global namespace. It's rarely referenced directly, as its contents are available without a prefix, for example __dirname instead of global.__dirname.

`globalThis`

🟢 Aliases to global.

`Headers`

🟢 Fully implemented.

`MessageChannel`

🟢 Fully implemented.

`MessageEvent`

🟢 Fully implemented.

`MessagePort`

🟢 Fully implemented.

`module`

🟢 Fully implemented.

`PerformanceEntry`

🟢 Fully implemented.

`PerformanceMark`

🟢 Fully implemented.

`PerformanceMeasure`

🟢 Fully implemented.

`PerformanceObserver`

🟢 Fully implemented.

`PerformanceObserverEntryList`

🟢 Fully implemented.

`PerformanceResourceTiming`

🟢 Fully implemented.

`performance`

🟢 Fully implemented.

`process`

🟡 Mostly implemented. process.binding (internal Node.js bindings some packages rely on) is partially implemented. process.title is a no-op on macOS & Linux. getActiveResourcesInfo setActiveResourcesInfo, getActiveResources and setSourceMapsEnabled are stubs. Newer APIs like process.loadEnvFile are not implemented.

Web-standard APIs supported by Bun for server-side JavaScript

Roadmap

Bun's roadmap and long-term plans

Node.js Compatibility

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