What this webcam test shows
Click “Start camera” and allow access: the test shows the live image right away, together with what your webcam actually delivers, namely resolution, aspect ratio, megapixels, the frame rate the driver reports and the measured frame rate. A resolution test requests 2160p down to 480p one step at a time. The image stays in your browser and nothing is uploaded.
Why is my webcam not working?
The browser reports every failure with a fixed name from the W3C specification “Media Capture and Streams”. The test translates that name and gives the fix:
| Browser message | Meaning | Fix |
|---|---|---|
| NotAllowedError | access denied | site settings (icon to the left of the address bar) or the camera permission in your operating system |
| NotFoundError | no camera found | check the cable and USB port, switch a camera back on that was turned off with a function key |
| NotReadableError | camera busy | close Zoom, Teams, OBS or other tabs with a video call |
| OverconstrainedError | selected camera unavailable | pick another camera or the default camera |
Without an encrypted connection there is no camera access at all: the same specification only exposes the camera interface in secure contexts, which means https. If the operating system blocks the camera, the tool points you to the privacy settings in Windows and macOS.
What resolution does my webcam really have?
The highest step the resolution test marks as “delivered”. It requests every step on its own and compares requested with received; a Full HD webcam answers a request for 2160p with 1920 × 1080. A browser can scale smaller steps down from a larger image. The test asks it not to, and Chrome follows that request. The highest step delivered is therefore the most telling result.
| Step | Pixels | Megapixels | Aspect ratio |
|---|---|---|---|
| 2160p (4K UHD) | 3840 × 2160 | 8.3 | 16:9 |
| 1440p (QHD) | 2560 × 1440 | 3.7 | 16:9 |
| 1080p (Full HD) | 1920 × 1080 | 2.1 | 16:9 |
| 720p (HD) | 1280 × 720 | 0.9 | 16:9 |
| 480p (VGA) | 640 × 480 | 0.3 | 4:3 |
1920 × 1080 is the HDTV image format of Recommendation ITU-R BT.709, 3840 × 2160 the UHDTV format of ITU-R BT.2020. The number before the “p” is the line count of the shorter side, and the “p” stands for progressive scan. A phone held upright delivers 1080 × 1920, which is 1080p as well.
Why does my webcam show fewer frames per second than stated?
The driver reports which frame rate is configured, not how many frames actually arrive. So the test
counts along: it records every new video frame via requestVideoFrameCallback and averages the gaps of
the last three seconds, leaving out pauses and single outliers. If the measured value is more than
10 percent away from the driver's figure, a note appears.
Low light is a typical reason. At 30 frames per second each frame can be exposed for at most 33.3 milliseconds; if the automatic exposure needs longer in the dark, the camera lowers its frame rate. A second reason is the cable: according to its specification, USB 2.0 carries at most 480 Mbit/s, while uncompressed 1080p at 30 frames per second would need about 995 Mbit/s at 16 bits per pixel. USB 2.0 webcams therefore compress the image or lower the frame rate.
How to use the test
- Start camera and choose “Allow” in your browser's prompt.
- If you have several cameras, pick the right one from the list; browsers only show the names after access is granted.
- Read the values. “Not reported” means the browser does not give out that value.
- Run resolution test if you want to know the most your camera delivers.
- Snapshot saves a full-resolution PNG, for comparing two cameras or for a support request.
- Stop camera, and it is free again for Zoom, Teams and other programs.
If the live image is almost black, the test points it out. Then check the lens: is a privacy shutter covering it, or was the camera switched off with a key?
Why is the picture mirrored?
The preview shows you like a mirror, the way many video call programs display your own image. Only the view is mirrored: what the camera delivers and what the snapshot saves are not. Untick “Mirror preview” to turn it off; for a phone's rear camera it starts switched off.
Privacy
The camera image never leaves your device. It runs from the camera into the browser, where it is displayed and measured; there is no recording and no server receiving anything. After “Stop camera” and when you leave the page, the tool closes every video track.