GEARCHECK LABCheck whether the captured microphone signal repeatedly approaches digital full scale when you speak normally. Start quietly and use your normal microphone distance.
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Peak dBFS describes the largest absolute sample captured by this browser, where zero dBFS is digital full scale. Samples at or above 0.99 absolute amplitude are counted as near full scale. The counter is evidence of very high digital level, not a calibrated diagnosis of analog distortion. A compressed or limited source can sound distorted without reaching that threshold. Repeat at the same distance and compare before and after changing input gain. The tool does not play your microphone through the speakers and creates no recording.
Browser processing and the microphone driver can alter the waveform. This cannot measure sound pressure, certify capsule health or prove the absence of analog clipping. Hiding the tab or Stop releases the microphone. Permission errors and missing devices are reported as unavailable rather than failed hardware.
Device previews, recordings, selected files and report notes stay in your browser. Downloaded files remain on your device. The call check sends small HTTP probes to GearCheck Lab. The WebRTC test exchanges temporary connection descriptions through our server and contacts the disclosed STUN service only after you create or join a session. Ordinary page requests and usage measurement are described in our privacy policy.