Allow microphone access. The page shows signal level, peak, clipping, sample rate, frequency spectrum and recording preview. Audio stays local in this browser.
Start requests microphone permission and activates the live waveform/spectrum and dBFS meter. Stop closes the stream. Record toggles a short local sample using the browser's MediaRecorder; the file extension follows the actual MIME type produced by the browser (WebM/Opus, OGG/Opus, or MP4 depending on platform).
Visualizer modes: Waveform shows time-domain amplitude (the classic oscilloscope view), Spectrum shows real-time FFT magnitude on a log frequency axis (20 Hz – 20 kHz), RMS history shows the recent dBFS envelope over time. Switch with the tabs above the canvas.
Stereo meters appear when the input track exposes 2 channels — useful for checking that both sides of a stereo headset/mic capsule are active.
Raw diagnostic mode is the default: echo cancellation, noise suppression and auto gain are off so the signal is unprocessed. Turn them on only to verify call-mode behavior.
Capabilities table lists what track.getCapabilities() exposes for the active input (sample rate range, channel count, latency, etc.). Empty means the device does not advertise constraints.
track.getCapabilities()
Keyboard shortcuts: Space play/pause recording · R record · S stop · F fullscreen · H hide/show side controls · 1/2/3 visualizer mode · ? help · Esc close dialog.
Privacy: the file makes no network calls (CSP connect-src 'none'). The microphone stream is never uploaded; export creates a local JSON report. Settings persist in localStorage under the mictest: prefix.
connect-src 'none'
localStorage
mictest:
Troubleshooting: microphone access requires HTTPS, localhost or a secure browser context. If permission is blocked, reset it from the browser site-permissions icon and press Start again.