The purpose of using “aria-labelledby” on already labeled input elements?

Question

Many ARIA demonstration websites use code such as:

Your Name


        

Answer 1

There's some good examples of its use at Mozilla Developer pages. Perhaps the best of their examples is where it's used to associate a popup menu with the parent menu item - it's Example 7 in the page:

  
    
File
  
    
  
        
Open
  
        
Save
  
       
Save as ...
  
       ...  
    
  
    ...  

ARIA attributes tends to be of greatest use in building Accessible Rich Internet Applications: so long as you're sticking with standard semantic HTML - using forms with standards labels - you shouldn't need it at all: so there's no reason to use it on a LABEL/INPUT pair. But if you're building "rich UI" from scratch (DIVs and other low level elements with javascript adding interactivity), then it's essential for letting a screenreader know what the higher-level intent is.