This flashes bright colors very fast. Don’t use it if you are sensitive to flashing light.
Clear image retention
This can fade temporary image retention, but it can’t fix permanent burn-in. Noise flickers fast, so skip it if flashing light affects you.
Screen light
Start test tones at a low volume, especially with headphones, and skip the pixel fixer and the noise pattern if flashing light affects you. These tests check your devices, not your hearing or eyesight.
Play a voice-like sound in the left, right or center channel to check stereo wiring and headphone sides in seconds. Switch to noise to compare the loudness of both sides, and run the phase test to catch a speaker with its + and − wires reversed.
How to use
- Pick a tab: Microphone, Webcam, Speakers or Screen.
- Microphone: press Test microphone and allow access. Speak — the meter, wave and status show whether sound arrives. Record 5 s to hear yourself.
- Webcam: press Start camera and allow access. The badge shows the real resolution and measured frames per second; switch cameras or resolutions below.
- Speakers: tap Left, Center or Right. Use the frequency slider or the sweep to check bass and treble.
- Screen: tap a color or start the full-screen test, then tap or press → to step through colors. Look for dots that don’t match.
- The browser asks for permission only after you press a start button. Audio and video never leave your device; recordings are kept in memory until you close the page.
- If no sound is detected, check the mute switch on your headset, the input level in your system sound settings and that the right device is selected.
- Out of phase should sound thin and hard to place. If In phase sounds that way instead, one speaker’s wires are swapped.
- A dead pixel stays black on every color; a stuck pixel stays red, green or blue. The fixer may help stuck pixels after 5–10 minutes, but it can’t repair dead ones.
Left, right and phase
The left and right buttons confirm that each channel plays from the correct side; if Left comes from your right ear, the headphones are on backwards or the cables are swapped. The phase test plays the same sound in both speakers, first in phase and then with one side inverted. In phase sounds full and centered; out of phase sounds thin, hollow and hard to place. If In phase sounds that way instead, one speaker's + and − wires are reversed, which also weakens bass.
Voice is easiest to place, noise is best for comparing loudness between sides, and a pure tone shows rattles and buzzes in a cabinet.
Frequency range and the sweep
Human hearing spans roughly 20 Hz to 20 kHz when young, and the upper limit drops with age, often to 14–16 kHz in middle age. The sweep glides from 20 Hz to 20 kHz in 20 seconds: note when you first hear the bass and when the treble disappears. Small laptop and phone speakers rarely play much below 100–150 Hz; a subwoofer reaches 30–40 Hz. Start at a low volume, especially with headphones, as high and low tones can be louder than they seem.
Frequently asked questions
How do I test left and right speakers?
Tap Left, then Right. Each sound should come only from that side. Center plays from both, so it should seem to come from the middle.
How do I know if my speakers are out of phase?
Play the phase test. If the In phase sound is thin and hard to locate while Out of phase sounds fuller, one speaker's wires are swapped.
What frequencies can humans hear?
About 20 Hz to 20 kHz for young people; the upper limit usually falls with age. Most speech is between 100 Hz and 4 kHz.
Why can't I hear the bass tones?
Small speakers and many headphones cannot reproduce very low frequencies. Below around 100 Hz phone and laptop speakers usually fall silent.
Can I choose which speaker or headphones to test?
In browsers that support output selection you can pick the device in the list; otherwise the sound plays through the system's default output.