guidelines - Truncating long text labels - Best Practices?

I was wondering whether there are any studies around truncated labels, in case if they ever get too long and layouts can't fix it? Does it confuse users if a label is truncated with an ellipsis character in the middle of a label like so:

• 
  

  LabelBeginning...LabelEnd

  
  

  or

  
  


• LabelBeginning (...) LabelEnd

If I compare different text style guidelines there are different approaches. Apple e.g truncates long labels with an ellipsis in the middle of a label, which I think is a great solution as I think it reflects how people scan and identify a label (beginning and end).

"An ellipsis character can also show that there is more text than there is room to display in a document title or list item. If, for example, the name of an item is too long to fit in a menu or list box, you should insert an ellipsis character in the middle of the name, preserving the beginning and the end of the name. This ensures that the parts of the name that are most likely to be unique are still visible."

Microsoft suggests to avoid truncating labels wherever possible, but doesn't go into detail in how to implement an ellipsis in long labels.

"Ellipses mean incompleteness. Use ellipses in UI text as follows:

• Commands. Indicate that a command needs additional information. Don't use an ellipsis whenever an action displays another window—only when additional information is required. Commands whose implicit verb is to show another window don't take an ellipsis, such as Advanced, Help, Options, Properties, or Settings.

• Data. Indicate that text is truncated.

• Labels. Indicate that a task is in progress (for example, "Searching...").

Tip: Truncated text in a window or page with unused space indicates poor layout or a default window size that is too small. Strive for layouts and default window sizes that eliminate or reduce the amount of truncated text. "

Answer

Summary: It depends, but default to 'abcdef...' over 'abc...def'

I would choose the method on the basis of whether text at the end or in the middle of the string is more likely to differentiate the item. This would be dependent on the domain (so I don't think isolated studies from particular contexts would be helpful).

On a property website, for instance, an address string will usually end 'Road' or 'Street'. So the form 'abc...def' won't be much use as the final characters will almost always be 'oad' or 'eet', neither of which help the user.

If the answer is not clear, I would then default to the 'abcdef...' form over 'abc...def'. This is because I strongly suspect that partial words will be easier to guess from the initial characters than the end ones. 'Openi...' is much more recognizable than '...ening', for example. This is because many English words have non-unique suffixes and ending patterns.