Gray Line on Screen

[boykale]

Hello. Today when I was surfing the internet, the gray line appeared on the top left of my monitor. I just turned off and turned on monitor but it was still there for at least 30 mins. After a while, when I was on some colored web pages, it disappeared automatically. Although I am not sure whether if this is about my monitor or GPU, I think it's probably about monitor. What is your opinions?

 

https://imgur.com/a/8SdAgQH

 

EDIT:

 

Well, I just tested my monitor with HDMI 2.0 cable. If I set the Hz to 144, when I scroll down in dark colored pages, I can see horizontal lines. If I set Hz to 120, the horizontal lines are always visible fixedly. If I set Hz to 100, there is no horizontal lines. This case is same with Displayport cable. I think it's visible scanline issue. Is that a defect?
 

The lines are more faint and look like this.

 

 

PC SPEC
GeForce RTX 2080 Duke 8G OC
Intel Core i7-9700K
MSI MPG Z390 Gaming Plus
Gskill 16 GB (2x8GB) SniperX DDR4 3200MHz CL16 1.35V

Corsair RM850X(2018)

[ManosMax13]

Do u have  a spare gpu.If so try again with another gpu installed.Same if you have another monitor

[boykale]

1 minute ago, ManosMax13 said:

Do u have  a spare gpu.If so try again with another gpu installed.Same if you have another monitor

I was going to try with another monitor however the gray line does not exist now.

[2SidedPolygon]

The fact that it went away after a while on its own while your attempts to solve it by restarting the monitor didn't fix it would suggest that it was something with the GPU. If the issues happens again, restart your PC and see if it's fixed. If it becomes recurring update/reinstall drivers.

[ManosMax13]

Just now, boykale said:

I was going to try with another monitor however the gray line does not exist now.

Ok you can try it anyways in case it returns.It may be the cable too so look out for that and make sure that it is tightly in place.

[boykale]

I also notice something about this new monitor. When I am in FPS game and move mouse fast vertically-horizontally or drag open tabs ie. discord circularly, I feel like I can see pixels line by line on dark colored areas. It's really hard to explain. I can clearly see it with discord tab as it's dark gray. That's what makes me think it may be something about this monitor.

[boykale]

Well, I just tested my monitor with HDMI 2.0 cable. If I set the Hz to 144, when I scroll down in dark colored pages, I can see horizontal lines. If I set Hz to 120, the horizontal lines are always visible fixedly. If I set Hz to 100, there is no horizontal lines. This case is same with Displayport cable. I think it's visible scanline issue. Is that a defect?
 

The lines are more faint and look like this.