Clap Test
Audio/Video Sync Test
Recorded lectures and streams often drift out of sync between audio and video — and testing each device separately never catches it. This uses your own clap as a shared reference point: it fires a cue, you clap once, and it measures the actual millisecond gap between the visual motion of your hands meeting and the sound hitting your mic.
Status
Run the Free Online Audio/Video Sync Test
Click "Start Sync Test", keep both hands visible in frame, and clap firmly once when prompted.
Readout
Lip Sync Offset Results & Diagnostics
Details
- Direction:—
- Verdict:—
- Video Spike Confidence:—
- Audio Spike Confidence:—
Resolution is limited to roughly one camera frame interval (~16–33ms depending on your webcam's frame rate) — this is a practical estimate, not a lab-grade measurement. Run it 2–3 times and look at the pattern rather than a single result.
Related Tools
Take This Further
Sync is only one dimension of audio quality. If your voice also sounds thin, boomy or noisy, run the full microphone and room acoustics test.
Notes
Where audio-video delay actually comes from
Your voice and your image travel separate paths before they reach the same timeline. Audio passes through a microphone, an audio interface or driver, and often a processing stage for noise suppression. Video passes through a sensor, an encoder, and a driver of its own. Each stage adds a small delay, and there is no mechanism ensuring the totals match.
Some contributors are large and predictable. Bluetooth audio adds substantial latency by design, because sound must be compressed, transmitted wirelessly, and decompressed at the other end. Others are surprising: a microphone with built-in noise suppression can add tens of milliseconds before the signal reaches your computer, and virtual backgrounds or beauty filters delay video specifically by adding computation between capture and encode.
Reading your result
Benchmark Reference
Sync Offset at a Glance
| Grade | Offset | Viewer experience |
|---|---|---|
| Excellent | ≤ 30 ms | Imperceptible — no fix needed. |
| Noticeable | 30 – 100 ms | Some viewers notice on close-up speech. |
| Distracting | > 100 ms | Viewers sense something is off, worth fixing. |
These bands sit in the same range broadcast engineers commonly target for acceptable lip sync, applied here to your own real measured offset.
Step-by-Step
How to Run the Test
- Click "Start" and allow camera and microphone access when prompted.
- Position your hands clearly in frame, ready to clap.
- Clap firmly once when the countdown ends — a single sharp, visible clap gives the cleanest reading.
- Read your offset and direction, then run it two or three more times to see the pattern rather than trusting one result.
Common Issues
Turning the Number Into a Fix
For live calls, the practical remedies are removing Bluetooth from the chain, disabling video effects, and closing applications competing for processing time. There is no offset control in most conferencing software, so reducing the delay at source is the only option.
For recording and streaming, the measurement is directly actionable. Most recording software lets you apply a fixed millisecond offset to a specific track — enter the figure this test reports and the drift disappears. That is considerably faster and more accurate than nudging tracks by eye in an editor afterwards.
Run the test two or three times before acting. A single measurement is limited by your camera's frame interval, so the pattern across several runs is more reliable than any one result.
Common Questions