I recently purchased a high-end 4K monitor for my home office setup, but I suspect there might be some minor issues with backlight uniformity, especially in the corners. I've noticed a bit of "glow" when watching dark scenes or working in dark-themed IDEs. I want to perform a manual display audit to check for dead pixels and backlight bleed without having to download or install complex diagnostic software that might contain bloatware.

Specifically, I am looking for a tool that can provide a 100% pure dark field. In addition to testing, I've heard that some professional editors use a total black display on their secondary monitors to eliminate peripheral distractions while they are focused on a main task.

Does anyone have experience with a reliable fullscreen black screen tool that works directly in the browser? I found one option and decided to try it here to see if it could help me identify these panel defects. It seems to work well for a quick "Digital Blackout," but I am curious if there are other web-based utilities that offer similar features for monitor calibration or focus enhancement.

How do you guys usually test your new monitors for defects, and do you think using a black screen to minimize visual noise actually helps with productivity during long work sessions? Any advice would be greatly appreciated!