This issue has been reported several times but incorrectly marked as duplicate or just closed with no explanation.
The terminal window should have under no circumstances a white border. Not just in dark mode but NEVER. It is completely inconsistent with all other Windows apps including those from Microsoft.






Issues that were incorrectly closed:
Btw ... aren't there any Microsoft design guidelines? I assume this issue shouldn't be discussed at all per application.
The border color is affected by a number of settings. Typically it uses the accent color, in which case it could be white (or at least a light gray) if that's the accent color you chose. But I suspect in this case you've probably just turned off _Title bars and window borders_ option, and that's what's responsible for the white border in the _Light_ mode.
I think that might be a bug, but it's different from the original white border issue.
Here is my setting:

This is because the Windows Terminal is a Win32 app with a custom title bar and Win32 apps with custom title bars have white borders by default:


Note that when I made the PR #3394 which added a custom title bar by removing the standard Win32 title bar, I did not change the default behavior of having that white border. Because the Windows Terminal wants to look like a UWP app, maybe this should be faked as well, like the title bar, by always making the border dark?
We could do this by chaging _OnNcCreate on NonClientIslandWindow to unconditionally set the black border, something like this:
I can make a PR that does this if the Windows Terminal team wants the black border.
I don't think it's meant to be black exactly. I suspect it might be version specific, but the border colors I'm seeing on most UWP apps is different on the top and sides, and it's actually a level of transparency, so what you see will depend on the background. I'm talking specifically about the _Light_ mode, with the _Title bars and window borders_ option disabled.
I'm on version 10.0.18362.836. The OP didn't fill in the bug template, so I don't know what version he is using, but his screenshots look different to what I'm seeing.
I am using Terminal 1.0.1401.0 (stable) and 1.1.1671.0 (preview). The issue is the same in both.
Here is my Windows version:

Yes sorry I meant "dark" instead of "black".
j4james, I don't know if you're talking about this when you say that the top and side colors are not the same, but if you are, I think it's a bug because it disappears after a restart:

(see how the top border is dark but other borders are light)
I am on 10.0.18362.900.
j4james, I don't know if you're talking about this when you say that the top and side colors are not the same, but if you are, I think it's a bug because it disappears after a restart:
That makes sense. That's exactly what I'm seeing. I thought it might be a bug.
This is unrelated to the OP but I reported this bug (with the UWP apps, not with the Windows Terminal, again not related to the OP) in the Feedback Hub: https://aka.ms/AA6pqh3.
Unfortunately, there isn’t a standard here. If somebody wants to remove the theme check around “TrySetDarkMode” in “NonClientIslandWindow.cpp”, I would absolutely accept that pull request.
Thanks for digging up all these counterexamples, @michalhudecek!
(When I say “there isn’t a standard here,” I mean “terminal even has to use a _private API_ to get its window borders to look like other UWP applications.” It drives me crazy!)
There is no standard even "on paper"? I mean something like a codified design system: https://atlassian.design/guidelines/product/overview or https://material.io/components
That was quick! Good job :)
:tada:This issue was addressed in #6624, which has now been successfully released as Windows Terminal Preview v1.2.2022.0.:tada:
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