How to resize Safari address bar on macOS Sierra or newer? It seems that the Safari address bar width is locked to a maximum size that may make some URL impossible to read, especially if the domain part is longer, like in many intranets, or when the the of the URL is longer and when it  contains essential information near the end.



I fount no way to change the width of the bar using Customize Toolbar option.
I am using Safari 11 on macOS 10.13 (high-sierra) but I am pretty sure that the same problem would apply for macOS 10.12 (Sierra).
Right-click on an empty area at the top of Safari’s window and select Customize Toolbar.
You’ll see two “flexible spaces” on each side of the URL bar. 2 tranparent boxes.
Remove these boxes (by dragging them out of the toolbar), and you should wind up with a larger URL entry area.