How to read the result
The bar shows how loud your microphone hears you. Talk at a normal volume from about an arm's length away and you want it bouncing around the middle. Barely moving? Your input level is too low, or the browser picked a different mic than the one you're talking into. Constantly hitting the red? It's set too high, and people on your calls will hear distortion.
The meter only tells you that sound is coming in, not whether it sounds good. For that, hit Record 5 seconds and listen back. Five seconds of your own voice will reveal what a meter can't: background hiss, an echo from a bare room, or that muffled sound you get when a headset mic is pointing at your cheek.
Mic not picked up at all?
Start with the browser. If you ever clicked "Block" on a permission pop-up, the site stays blocked until you change it yourself. Look for the small lock or microphone icon in the address bar. Then check the dropdown above the meter. A laptop with a headset plugged in can easily list three or four inputs, and the default isn't always the one you're using.
Windows 10 and 11. Open Settings > Privacy & security > Microphone and make sure microphone access is on, including access for desktop apps. Then go to Settings > System > Sound, pick your mic under Input and check its volume. A very common culprit is another app holding on to the mic. Discord, Teams and Zoom can all do this, even when they're minimized. Close them fully and test again.
macOS. Open System Settings > Privacy & Security > Microphone and switch your browser on. If you only just did that, quit the browser completely with Cmd+Q and open it again. macOS doesn't apply the change to an app that's already running.
Android and iPhone. On Android, long-press your browser's icon, tap App info > Permissions > Microphone. On iPhone, open Settings, find Chrome or Safari and check that Microphone is allowed.
Bluetooth headset sounds terrible?
Your headset probably isn't broken. As soon as a Bluetooth headset uses its microphone, most computers switch it to a hands-free mode that drops the audio quality to phone-call level. Your voice sounds like it's coming through a tin can, and music playing at the same time suddenly sounds flat. It's a limitation of how Bluetooth handles audio in both directions. A wired headset or a USB microphone doesn't have this problem.
Setting up for calls? The webcam test checks your camera the same way, and a quiet room with good light in front of you helps both.
How this test works
When you click Start, your browser asks for permission and then passes the microphone signal to this page. On every screen refresh the test takes the latest slice of sound, works out how loud it is in decibels and moves the bar: it jumps up straight away and falls back slowly, like the meter on a mixing desk. The panel below the bar draws the signal itself, so you can see it react as you speak.
Nothing leaves your device. Record 5 seconds keeps the clip in your browser's memory only, and it is gone the moment you refresh or close the page.