# web-audio-api > Pure JavaScript Web Audio API for Node, CI, and servers Latest version **1.5.6** (published 2026-09-06) · MIT license · 0 weekly downloads ## Install ```sh npm install web-audio-api pnpm add web-audio-api yarn add web-audio-api bun add web-audio-api ``` Provides the command `web-audio-api`. ## Health **Score 70/100 (B)** — status: active. Positive: has types; esm support; no vulnerabilities; recently updated; high maintenance score; high quality score. Warnings: low downloads. ## Facts | | | |---|---| | Version | 1.5.6 | | Published | 2026-09-06 | | First published | 2013-07-31 | | Weekly downloads | 0 | | License | MIT | | TypeScript types | bundled | | Module format | ESM | | Node | >=18 | | Dependencies | 9 | | Unpacked size | 590.2 KB | | Known vulnerabilities | 0 | | Install scripts | no | | GitHub stars | 949 | | Author | Sébastien Piquemal | | Maintainers | dfcreative, sebpiq, jamen, dy | | Keywords | audio, audiojs, sound, music, web audio, web audio api, waa, dsp | ## Links - npm: https://www.npmjs.com/package/web-audio-api - Repository: https://github.com/audiojs/web-audio-api - Homepage: https://audiojs.dev/web-audio-api/ - Issues: https://github.com/audiojs/web-audio-api/issues - Funding: https://github.com/sponsors/audiojs - npm.io page: https://npm.io/package/web-audio-api ## Dependencies (9) - [pcm-convert](https://npm.io/package/pcm-convert.md) ^3.1.1 - [audio-buffer](https://npm.io/package/audio-buffer.md) ^7.3.0 - [audio-effect](https://npm.io/package/audio-effect.md) ^1.0.0 - [@audio/decode](https://npm.io/package/@audio/decode.md) ^3.15.0 - [@audio/speaker](https://npm.io/package/@audio/speaker.md) ^2.3.3 - [digital-filter](https://npm.io/package/digital-filter.md) ^2.3.0 - [automation-events](https://npm.io/package/automation-events.md) ^7.1.19 - [fourier-transform](https://npm.io/package/fourier-transform.md) ^2.2.0 - [periodic-function](https://npm.io/package/periodic-function.md) ^2.1.0 ## Recent versions - 1.5.6 (latest) — 2026-09-06 - 1.5.5 — 2026-09-02 - 1.5.4 — 2026-08-28 - 1.5.3 — 2026-07-11 - 1.5.2 — 2026-07-10 - 1.5.1 — 2026-05-09 - 1.5.0 — 2026-05-02 - 1.4.0 — 2026-04-29 - 1.3.4 — 2026-04-25 - 1.3.3 — 2026-04-09 - 1.3.2 — 2026-03-31 - 1.3.1 — 2026-03-31 - 1.3.0 — 2026-03-31 - 1.2.0 — 2026-03-20 - 1.1.1 — 2026-03-20 - … 10 more at https://npm.io/package/web-audio-api/versions ## README # web-audio-api [![W3C WPT](https://github.com/audiojs/web-audio-api/actions/workflows/wpt.yml/badge.svg)](https://github.com/audiojs/web-audio-api/actions/workflows/wpt.yml) [![platforms](https://github.com/audiojs/web-audio-api/actions/workflows/platforms.yml/badge.svg)](https://github.com/audiojs/web-audio-api/actions/workflows/platforms.yml) [![npm](https://img.shields.io/npm/v/web-audio-api)](https://npmjs.org/package/web-audio-api) [Web Audio API](https://audiojs.dev/web-audio-api/) pure JavaScript implementation. Useful for: * **Server-side rendering** – reuse Web Audio graphs with `OfflineAudioContext`. * **Audio in CI** – render and assert on samples in Node, Deno, and Bun. * **Audio analysis** – `decodeAudioData` for 20+ formats, `AnalyserNode` as in browser. * **Agents and bots** – write PCM to streams, no audio device needed. * **Compatibility testing** – a fully passing checked-in [WPT corpus under our Node runner](test/WPT.md). * **Tone.js and web audio libs** – `import 'web-audio-api/polyfill'` installs the globals. * **CLI audio scripting** – PCM in and out through stdio, 46 runnable examples. ``` npm install web-audio-api ``` ## Use ```js import { AudioContext } from 'web-audio-api' const ctx = new AudioContext() await ctx.resume() const osc = ctx.createOscillator() osc.frequency.value = 440 osc.connect(ctx.destination) osc.start() // → A440 through your speakers ``` [`@audio/speaker`](https://github.com/audiojs/speaker) provides device output through platform-specific backends, including native dependencies. The DSP engine itself is JavaScript.
How do I render offline, without speakers? ```js import { OfflineAudioContext } from 'web-audio-api' const ctx = new OfflineAudioContext(2, 44100, 44100) // 1 second, stereo const osc = ctx.createOscillator() osc.frequency.value = 440 osc.connect(ctx.destination) osc.start() const buffer = await ctx.startRendering() // buffer.getChannelData(0) → Float32Array of 44100 samples ``` Rendering runs as fast as the graph and host allow and opens no audio device, so it can run in a test runner for asserting on samples. See [render-to-buffer.js](examples/render-to-buffer.js).
How do I close an AudioContext? ```js await ctx.close() ``` Or with [explicit resource management](https://github.com/tc39/proposal-explicit-resource-management): `using ctx = new AudioContext()`
Why does it start suspended? `AudioContext` starts suspended to match the [Web Audio lifecycle](https://webaudio.github.io/web-audio-api/#dom-audiocontext-audiocontext). In Node, call `await ctx.resume()`. Browsers may require that call inside a user gesture. `OfflineAudioContext` doesn't need it.
Does it work with Tone.js? Yes. Tone.js uses `standardized-audio-context`, which needs globals such as `window.AudioParam` for `instanceof` checks. Load the polyfill before Tone.js: ```js import 'web-audio-api/polyfill' const Tone = await import('tone') Tone.setContext(new AudioContext()) const synth = new Tone.Synth().toDestination() synth.triggerAttackRelease('C4', '8n') ``` Tone.js must use a dynamic `import()` because static imports run before the polyfill. Alternatively, use `--import`: ```sh node --import web-audio-api/polyfill app.js ``` Then static `import * as Tone from 'tone'` works in `app.js`.
How do I decode audio files? ```js const buffer = await ctx.decodeAudioData(readFileSync('track.mp3')) ``` `decodeAudioData()` uses [@audio/decode](https://github.com/audiojs/decode) for MP3, WAV, Ogg Vorbis, Opus, FLAC, AAC, ALAC, AIFF, CAF, WebM, and other supported audio or video containers without FFmpeg or native bindings.
How do I capture audio from the microphone? In Node, pair [`@audio/mic`](https://github.com/audiojs/mic) with `CustomMediaStreamTrack`: ```sh npm install @audio/mic ``` ```js import { AudioContext, MediaStreamAudioSourceNode, CustomMediaStreamTrack, MediaStream } from 'web-audio-api' import mic from '@audio/mic' const ctx = new AudioContext() await ctx.resume() const track = new CustomMediaStreamTrack({ kind: 'audio', label: 'mic', settings: { channelCount: 1, sampleSize: 16, sampleRate: ctx.sampleRate } }) const stream = new MediaStream([track]) const src = new MediaStreamAudioSourceNode(ctx, { mediaStream: stream }) src.connect(ctx.destination) // live monitor // @audio/mic's read(cb) is single-shot; re-arm it inside the callback. const read = mic({ sampleRate: ctx.sampleRate, channels: 1, bitDepth: 16 }) const pump = () => read((err, buf) => { if (err || !buf) return track.pushData(buf, { channels: 1, bitDepth: 16 }) pump() }) pump() ``` `track.pushData()` accepts `Float32Array`, `Float32Array[]`, or interleaved 8/16/32-bit integer PCM buffers. Integer PCM conversion uses `pcm-convert`. `CustomMediaStreamTrack` extends `MediaStreamTrack`. Prior art: `CanvasCaptureMediaStreamTrack`. See [examples/mic.js](examples/mic.js) for a runnable demo with gain and VU meter. To record the graph to a buffer, use `OfflineAudioContext.startRendering()`. To capture live graph output as a stream, use `ctx.createMediaStreamDestination()`. If the default microphone backend cannot open the device, pass `backend: 'process'` to use `sox`/`ffmpeg` instead: `mic({ ..., backend: 'process' })`. All bundled examples accept `backend=process` on the command line.
How do I use it as a polyfill? ```js import 'web-audio-api/polyfill' // AudioContext, GainNode, etc. are now global ``` The polyfill also installs `navigator.mediaDevices.getUserMedia({ audio: true })`, backed by the optional [`@audio/mic`](https://github.com/audiojs/mic) peer dependency. This lets browser mic-capture code run verbatim in Node: ```js import 'web-audio-api/polyfill' // npm install @audio/mic const stream = await navigator.mediaDevices.getUserMedia({ audio: true }) const ctx = new AudioContext() const src = ctx.createMediaStreamSource(stream) src.connect(ctx.destination) // stop capture stream.getAudioTracks()[0].stop() ``` Without `@audio/mic` installed, `getUserMedia` rejects with a `NotFoundError` containing an install hint.
## Examples `node examples/.js` runs each example with its defaults. `node examples/.js --help` for every accepted argument, option, keyboard control, and alternate invocation. ### Test signals * [tone.js](examples/tone.js): Reference pitch – `sine A4 2s` * [sweep.js](examples/sweep.js): Hear the audible range – `20..20k exp 3s` * [noise.js](examples/noise.js): White, pink, brown, blue, violet – `pink 2s` * [impulse.js](examples/impulse.js): Dirac click – `5 0.5s` * [dtmf.js](examples/dtmf.js): Dial a phone number – `5551234` * [stereo-test.js](examples/stereo-test.js): Left, right, center – `1k 1s` * [metronome.js](examples/metronome.js): Programmable stick click – `80..240 10m X-x-x-x-` * [tuner.js](examples/tuner.js): Guitar tuner – mic pitch in cents – `440` (requires [`@audio/mic`](https://github.com/audiojs/mic)) * [latency-tester.js](examples/latency-tester.js): Round-trip latency: speakers → mic, in ms (requires [`@audio/mic`](https://github.com/audiojs/mic)) * [level-meter.js](examples/level-meter.js): Mic RMS and peak in dBFS, fast or slow ballistics (requires [`@audio/mic`](https://github.com/audiojs/mic)) ### Illusions * [shepard.js](examples/shepard.js): Pitch that rises forever – `up 15s` * [risset-rhythm.js](examples/risset-rhythm.js): Beat that accelerates forever – `up 120 20s` * [binaural-beats.js](examples/binaural-beats.js): Third tone from two (headphones!) – `200 10 10s` * [missing-fundamental.js](examples/missing-fundamental.js): Your brain fills in the note – `100 3s` * [beating.js](examples/beating.js): Two close frequencies dance – `440 3 5s` * [octave-illusion.js](examples/octave-illusion.js): One tone jumps register and side (headphones!) – `400 800 2 12s` * [scale-illusion.js](examples/scale-illusion.js): Two scales split between ears, regrouped by pitch (headphones!) – `200 261.63 8s` * [tritone-paradox.js](examples/tritone-paradox.js): Up or down? Tritone pairs that refuse to decide – `0 8 1.2` * [continuity.js](examples/continuity.js): A tone sounds unbroken through noise bursts – `440 0.6 on 15s` * [streaming.js](examples/streaming.js): Two tones fuse into one stream or split into two – `240 4 15s` * [huggins-pitch.js](examples/huggins-pitch.js): A pitch that exists in neither ear (headphones!) – `600 20s` * [zwicker-tone.js](examples/zwicker-tone.js): An after-tone lingers where the notch was – `2000 3 2 20s` ### Synthesis * [subtractive-synth.js](examples/subtractive-synth.js): Sawtooth → filter sweep → ADSR * [additive.js](examples/additive.js): Waveforms from harmonics – `square 220 16 3s` * [fm-synthesis.js](examples/fm-synthesis.js): DX7 frequency modulation – `440 2 5 3s` * [karplus-strong.js](examples/karplus-strong.js): A string plucked from noise – `A4 4s` * [wavetable.js](examples/wavetable.js): Fourier wavetables, crossfaded – `organ 220 0.3 6s` * [granular.js](examples/granular.js): Grain cloud from a seeded buffer – `0.08 15 4 10s` ### Generative [Musical models, styles, and offline listening fixtures](examples/MUSIC.md). * [sequencer.js](examples/sequencer.js): Step sequencer – precise timing * [serial.js](examples/serial.js): Twelve-tone rows (Webern) – `72 30s` * [gamelan.js](examples/gamelan.js): Balinese kotekan – two parts, one melody – `120 20s` * [drone.js](examples/drone.js): Tanpura, pads, or cinematic strings – `voice=strings melody=pentatonic freq=D3 -d 30s` * [jazz.js](examples/jazz.js): Jazz in seven styles, modal first, lead on guitar, flute, harp, or piano – `style=ambient lead=harp` * [euclidean.js](examples/euclidean.js): Bjorklund rhythms, 2–3 voices – `120 16 3,5,7 20s` ### API * [speaker.js](examples/speaker.js): Hello world * [lfo.js](examples/lfo.js): Tremolo via LFO * [spatial.js](examples/spatial.js): Sound moving through space * [worklet.js](examples/worklet.js): Custom AudioWorkletProcessor * [linked-params.js](examples/linked-params.js): One source controlling many gains * [fft.js](examples/fft.js): Frequency spectrum * [render-to-buffer.js](examples/render-to-buffer.js): Offline render → buffer * [process-file.js](examples/process-file.js): Audio file → EQ + compress → render * [pipe-stdout.js](examples/pipe-stdout.js): PCM to stdout – pipe to `aplay`, `sox`, etc. * [mic.js](examples/mic.js): Live microphone → speakers with RMS meter (requires [`@audio/mic`](https://github.com/audiojs/mic)) * [recorder.js](examples/recorder.js): Record the mic to a WAV file, with a level meter (requires [`@audio/mic`](https://github.com/audiojs/mic)) * [reverb.js](examples/reverb.js): Convolver with a seeded impulse response – `2 0.35 3s` ## Performance Run `npm run bench:compare` for an offline-render comparison with `node-web-audio-api`. The runner alternates engines after warmup and reports median and p95 times over 50 renders. [Saved results](benchmark/results.json) include raw samples, hardware, and versions. These are short offline graphs, not audio-device latency measurements or realtime guarantees. Measure your own graph and deployment host. ## Architecture Pull-based audio graph. `AudioDestinationNode` pulls upstream via `_tick()`, 128-sample render quanta per spec. AudioWorklet runs synchronously (no thread isolation). DSP kernels separated from graph plumbing for future WASM swap. ``` EventTarget ← Emitter ← DspObject ← AudioNode ← concrete nodes ← AudioParam EventTarget ← Emitter ← AudioPort ← AudioInput / AudioOutput ``` ## Node extensions Beyond the spec, for Node.js. Not portable to browsers. - **`addModule(fn)`** – register a processor via callback instead of URL, no file needed - **`sinkId: stream`** – pipe PCM to any writable: `new AudioContext({ sinkId: process.stdout })` then `node synth.js | aplay -f cd` - **`numberOfChannels`, `bitDepth`** – control output format in the constructor. - **`CustomMediaStreamTrack`** – extends `MediaStreamTrack` with a public constructor and `pushData(chunk, options)` to feed audio data (e.g. from a microphone). Prior art: `CanvasCaptureMediaStreamTrack`. See the [mic FAQ](#how-do-i-capture-audio-from-the-microphone). ## Alternatives - **[node-web-audio-api](https://github.com/ircam-ismm/node-web-audio-api)** – Rust DSP with Node bindings and native prebuilds; its browser export uses native Web Audio. Compare on your graph, especially when realtime performance matters. - **[standardized-audio-context](https://github.com/chrisguttandin/standardized-audio-context)** – Browser-only. Normalizes cross-browser quirks. - **[web-audio-api-rs](https://github.com/orottier/web-audio-api-rs)** – Pure Rust / WASM. - **[web-audio-engine](https://github.com/mohayonao/web-audio-engine)** – Archived. Partial spec coverage. - **[react-native-audio-api](https://github.com/software-mansion/react-native-audio-api)** – React native partial implementation. ## License MIT

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