I enjoy using the column view in the macOS Finder, but more more often than not, I need to resize the columns to be able to read all the file or folder names.
Certainly, resizing is easily done by dragging the vertical column separators to the right until all names are readable. What has been bugging me, however, is that when I do that for the right-most column, I often end up inadvertently resizing the window at the same time.
How to resize the right-most column without resizing the window?
It turns out, you can Ctrl-click (or right-click) on a column separator to open a context menu:
There you can chose to:
Right Size This Column to resize the column to the left of the separator;
Right Size All Columns Individually to resize all columns such that they are just as wide as they need to be to be able to read all file and folder names;
Right Size All Columns Equally to resize all columns such that they are all equally wide and readable.
So, if you chose one of the Resize All Columns… options, the right-most column will be resized. But, if you had selected the right-most separator, the window may still resize!
Therefore: Ctrl-click on one of the other column separators, not the right-most one. When resizing is initiated there, the window size will not be changed.
Finally, here is the best part:
This also works in a standard macOS "File Open" or "Save As" dialog!
[2019-08-16] You can also double-click on the column separator with your mouse:
Double-click on the column separator to Right Size This Column.
Option+Double-click on the column separator to Right Size All Columns Individually.