[palsecam]

Yes, but that can be surprising.

That you cannot adjust the z-index is disturbing, especially given that you have to style <dialog> yourself if you wanna make it look any good (as others have reported here).

Also, for the record, alert() is still higher than <dialog> on the plane (see https://i.imgur.com/tzKOEF2.png).

[Sesse__]

FWIW, it's on a separate layer that's not affected by z-index:

https://developer.mozilla.org/en-US/docs/Glossary/Top_layer