Start with a clean baseline
Visual inspection patterns can expose pixel, uniformity, gradient, scaling and motion symptoms, but they cannot replace a colorimeter or electrical display analyzer.
Live evidence
Relevant checks
Device & Browser Information CheckSee browser-exposed screen, viewport, language, CPU-thread class, memory class, connection hints, and platform information without installing software.
→WebUSB Device TestRequest a compatible USB device through WebUSB and display the browser-exposed manufacturer, product, vendor, and product IDs.
→Screen Share TestVerify that your browser can open the screen/window/tab sharing picker and start a local capture stream.
→First sequence
Do the high-signal checks before risky changes
- 1
Define whether you need charging, data, display or Thunderbolt
- 2
Try a known-good cable rated for that function
- 3
Test the attached device directly if possible
Decision points
What the result should change
If the defect stays in the same physical pixel/location across contentPrioritize panel/pixel/backlight hardware.
If the defect appears only at one resolution/refresh ratePrioritize cable, port, GPU/display mode or bandwidth.
If a screenshot contains the defect on another displayThe problem is upstream of the panel itself.
Browser can help check
- Test some attached USB devices
- Confirm browser-visible cameras/audio/input devices downstream
Browser cannot prove
- Read cable e-marker capabilities generically
- Measure USB Power Delivery negotiation
- Prove Thunderbolt lane/link health
Repair boundary
Know when to stop browser troubleshooting
- Do not open displays with exposed high-voltage power sections.
- Backlight bleed and uniformity are visual judgments affected by brightness and room lighting.
- HDR/color accuracy claims require appropriate instruments and controlled targets.
Used-device inspection
What to verify before paying or signing off a repair
- Full-screen dead/stuck pixel inspection
- Native resolution and intended refresh rate
- Inputs, cable compatibility, uniformity and text sharpness