Microphone level. The meter shows loudness in dBFS, where 0 is the loudest a digital signal can be. Normal speech at a sensible distance should peak between about −20 and −6 dBFS: the bar reaches the green-to-amber zone as you talk and falls back to almost nothing when you stop. A bar that never moves usually means the wrong device is selected, the mic is muted in the operating system, or a physical mute switch is on. Peaks that hit 0 dBFS (red) will sound distorted to others — move back or lower the input gain in your system settings.

Record and play back. This is the honest test: it captures five seconds and plays it through your speakers so you hear what a call would hear — room echo, keyboard clatter, a fan. The recording is held in memory only and discarded when you leave the page.

Speakers. The tones are generated on the device with the Web Audio API — there is no audio file and no download. If "Left" comes from the right side, your headphones are on backwards or the cable is reversed. If "Both" plays but one side is silent on a call, check the balance slider in your OS sound settings. The sweep rises from 40 Hz to 16 kHz over ten seconds; most adults stop hearing it somewhere between 12 and 17 kHz, and small laptop speakers cannot reproduce much below 150 Hz — neither is a fault.

Camera. The resolution and frame rate shown are what the browser actually negotiated, which is often lower than the box says (720p at 30 fps is typical). Video-call apps then compress further. Snapshots are saved straight to your downloads; nothing is transmitted.

Permissions. Browsers only allow microphone and camera access on secure (https) pages and after you click Allow; if you clicked Block once, look for the camera or padlock icon in the address bar to reset it. Safari on iPhone stops the camera when the tab is hidden — that is normal.