Side Nav no scroll bar unless height is given?

HTML-CSS
1

Can someone please explain why the scroll bar does not appear on the below unless I put in the height? Any insight appreciated…

#navbar{
    position:fixed;
    top:0px;
    left:0px;
    width:30%;
    //height:100vh why does scrollbar disappear??
    border-right: 2px solid var(--border-color);
    
    
}
2

Without seeing all of your code I can only guess here, but if you put a height of 100vh on it then you are telling it to stretch the entire height of the view port, which is taller than the natural height of the navbar and thus there is no need for a vertical scroll bar.

Again, I am just guessing. If you want better help then you’ll need to provide us a link to the project.