How does this green-screen test work?
We capture your webcam feed into a canvas at full frame rate and run an HSL chroma-key per pixel. Any pixel within the chosen tolerance of the picked key colour — default hue 120° for green — becomes transparent, revealing a checkerboard behind you. A live histogram of the green channel tells you whether your screen is evenly lit. The whole pipeline runs locally in your browser; the camera frames are never sent to a server or recorded.
The browser will not let me access the camera. How do I fix it?
Click the camera icon in your address bar and choose Allow for devicecheckonline.com. In Chrome and Edge, settings → Privacy and security → Site settings → Camera lets you unblock the site permanently. On macOS, also confirm your browser is allowed in System Settings → Privacy & Security → Camera. If Zoom, Teams or OBS is already holding the camera, close them — only one application can read a webcam at a time on Windows.
What makes a green screen key cleanly?
Even lighting is the single biggest factor. Light your screen separately from yourself with two soft sources at 45°, aiming for less than one f-stop variation across the cloth. Stand at least 1.5 metres in front of it to avoid green spill on your shoulders and hair. Iron out wrinkles — every fold creates a shadow that the keyer reads as a different colour. A matte fabric beats shiny vinyl. If the histogram shows a wide green peak instead of a tight spike, your lighting is uneven.
What is a good tolerance value?
Anything under 25 is excellent — it means your screen is evenly lit and your edges will be crisp in OBS, Zoom or Streamlabs. Tolerance 25 to 40 is acceptable for casual streaming; 40 to 60 indicates lighting problems that will show as green halos around hair and fingers. Above 60 and you will start to key out parts of your skin and clothing. Lower tolerance first, then adjust lighting until the key looks clean at the lowest value possible.
How does this relate to the other webcam tools?
This page focuses on chroma-key quality under your current lighting. To verify your camera can deliver the resolution and frame rate your streaming software needs, run devicecheckonline.com/webcam/resolutions. To check live FPS, exposure and codec while you adjust lights, use devicecheckonline.com/webcam/preview. Together they cover the full webcam pipeline from hardware capability through to production-ready keying.