Webcam Latency Test

The webcam latency test measures how much time passes from the moment your webcam captures an image to the moment you see it on screen. It also shows the real number of frames per second, the jitter between frames and how many frames are dropped along the way.

Two ways of measuring

The tool combines two independent measurements, because each sees a different part of the video path.

Measurement 1: frame metadata (automatic)

Once the camera is on, the browser reports for every frame when it was captured and when it is due on screen. From those timestamps the tool calculates:

• capture → display: the median time from capturing a frame to its scheduled display,
• capture → page script: when the frame becomes available to the page (important for apps that analyse the image, such as background effects in video calls),
• actual frames per second: from the median interval between consecutive frames, not from the driver's declaration,
• jitter: the difference between the 95th percentile and the median interval; the smaller it is, the smoother the picture,
• dropped frames: frames the camera delivered but the browser did not manage to show.

Capture time is reported by Chromium-based browsers (Chrome, Edge, Opera). When the browser does not provide it, the tool says so instead of guessing.

Measurement 2: optical loop, screen → camera

This measures the entire path, including the monitor. A box on the page switches from black to white and back, and the camera pointed at the screen has to see that change. The tool measures the time from the colour change to the frame in which the centre of the image became brighter or darker. It first calibrates the brightness of the black and the white box, then runs 10 cycles at random intervals and reports the median.

How to run the optical loop

1. Click "Turn camera on" and allow the browser to access it.
2. Point the camera at the black-and-white box. Just turn an external camera towards the screen; with a laptop, place a small mirror in front of the screen.
3. Position the camera so the box fills the dashed frame in the middle of the preview. The brightness bar under the preview helps: it should be short for the black box and long for the white one.
4. Click "Measure loop" and keep the camera still for a dozen seconds or so. If the brightness difference is too small, the tool stops and tells you what to fix.

What adds up to camera latency

• showing the change: the monitor displays the new colour on its next refresh, and its electronics add their own processing,
• exposure: a frame collects light for part of the frame interval; in the dark the camera lengthens exposure and often lowers the frame rate,
• waiting for a frame: the change lands at a random point of the camera cycle, so it waits half a frame interval on average,
• readout, compression and transfer: the camera compresses the image (usually MJPEG or H.264) and sends it over USB,
• decoding in the computer: the system and the browser unpack the frame and pass it on for display.

Frame interval and latency

The frame rate alone sets a lower bound for latency: a change on screen may wait up to a full interval for the camera's next frame.

The tool rates the loop result in three bands: up to 120 ms is low latency, up to 200 ms is medium, and above 200 ms is high. These are practical thresholds: in a video call, image latency adds up with network latency on both ends.

How to reduce webcam latency

• Add light to your face or scene. In poor light the camera lengthens exposure, which increases latency and lowers the frame rate.
• Choose a lower resolution if the camera drops to fewer frames per second at a higher one. Compare results for 640 × 480, 1280 × 720 and 1920 × 1080.
• Connect the camera directly to the computer, not through a USB hub; for Full HD use a USB 3 port.
• Close other programs using the camera, because two programs at once can lower the frame rate.
• Watch dropped frames. If they keep rising, the CPU cannot keep up with decoding; close heavy browser tabs.

You can check the picture, resolution and available cameras with the camera test, and keyboard and mouse latency with the input lag test.