What is this vertical black bar in Chrome on OS X?

Post date: 2020-09-25 16:59:23

In full-screen, on OS X in Chrome I have this vertical bar. It is not in the DOM, as I have selected hide element on the entire HTML tag. Extensions are not impacting it and shows up in Incognito mode. Sometimes it is on the top as in the screenshot, sometimes it is 3/4 of the way down. What is this?!

It doesn't seem to be impacting anything. I don't know enough about Chrome or native OS X apps to begin to debug the app itself but if someone wants to point out ways to debug this I have xtools and multiple other tools installed.

- Big Sur Beta 8, I don't feel like rolling back the OS to do further testing.
- Version 85.0.4183.121 (Official Build) (64-bit)
- Sometimes it is towards the top like in the screenshot, sometimes it is near the bottom. It appears to only have two states.
- Happens on all pages, including whatever the Intro or blank New Tab page is called.
- Cursor pointer appears OVER the black black so I assume this means it is definitely something Chrome is rendering.
- Has happened for the last 2 weeks or so that I noticed it. To be fair it is so inconspicuous especially when not viewing against a white background I could have just started noticing it.

I'm willing to provide any further bug reports. It appears Chrome may or at least used to use Cocoa and I have zero idea how to debug that. I see there's a pretty extensive Chromium page on it that looks arduous but I'm willing to try whatever as this is becoming a bit of a white whale for me.

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