efaq: Emacs ignores frame parameters
6.7 Why don’t my customizations of the frame parameters work?
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This probably happens because you have set the frame parameters in the
variable ‘initial-frame-alist’. That variable holds parameters used
only for the first frame created when Emacs starts. To customize the
parameters of all frames, change the variable ‘default-frame-alist’
instead.
These two variables exist because many users customize the initial
frame in a special way. For example, you could determine the position
and size of the initial frame, but would like to control the geometry of
the other frames by individually positioning each one of them.