Recorder JS

Recorder.js is a browser-based audio recorder for developers. It captures microphone input, buffers PCM samples in memory, and exports a WAV (PCM 16-bit) blob for playback, analysis, or download. The tool operates entirely client-side, avoiding server-side encoding and enabling offline processing when network access is limited. It is well suited for voice notes in language-learning apps, in-app recording features in web dashboards, and lightweight audio demos for demonstrations.

Conceptually, recording uses getUserMedia to access the microphone, an AudioContext to route audio into a PCM buffer, and a small WAV encoder to package samples with the proper header. The encoder runs in JavaScript with no external dependencies, producing a widely compatible WAV file. The API preserves explicit sampleRate and channelCount metadata, and reports duration and size alongside the output blob.

Core differentiators include a self-contained WAV encoder, a minimal configuration surface for sampleRate and channels, and a clean export API that returns both the Blob and accompanying metadata. Optional enhancements include stereo capture, adjustable bufferSize, and the ability to export partial recordings. Use cases span language practice, lab data collection, podcast snippets, and interactive tutorials.

Limitations and edge cases: encoding beyond WAV (such as MP3) is not included; streaming long sessions should be segmented or exported at stop to avoid memory spikes. The tool relies on browser support for MediaDevices and Web Audio; permission denial, device unavailability, or suspend/resume cycles must be handled gracefully by the consumer code. When no sound is captured, the resulting blob may be empty or very small.