In the diagram editor I am developing users can delete most of the nodes in the diagram, except a central node that is treated specially and can't be deleted. To block the user from deleting this node I have two options:

  1. Disable the option to delete a node when the special node is selected
  2. Show an error message to the user when he executes a command to delete the special node

While the first option is simpler to implement, I am worried that the users will be confused and will ask themselves why the command is disabled. Having it enabled with an error if executed removes this cognitive load from the user (my opinion).

Which of the two is the best customer experience?


4 Answers 4


The first option is the best. It's poor UX to invite someone to do something, and then tell them they can't do it. Think about Donald Norman's concept of 'Affordance'. A handle tells people that they can pull a door, while a plate tells them that they can push it. Your are giving people a handle on a push door here.

Use a common pattern, like greying out the option. Consider putting a rollover, with a brief explanation, if you find users don't understand it.

  • It is definitely frustrating, as a user, to be allowed to fail. You're right that a user should not be allowed to click the button and receive an error message. However, it will be important to provide feedback as to why. It could be a tooltip when the 'delete' is hovered, or some kind of message that displays near the element. Either way, the user has to be informed of why they cannot delete the node.
    – tonytrucco
    Aug 19, 2015 at 13:57

To disable the option is a general way to go, is more appropriate considering that you should always work towards error prevention. My suggestion is to clearly change the appearance of the non-deletable node in comparison with the default ones, and additionally show a tooltip or something indicating why this node is special and cannot be deleted. Over time using your editor, the users will recognise this differences and naturally learn how your editor works.


If something isn't going to be clear to the user then you better make it clear.

Why the central node cannot be deleted may be considered as 'invisible logic'. Thus, it is better to show an error message than to disable the action.

This is in contrast to disabled 'post comment' buttons that are enabled so long there is some text in the comment - users can infer that they cannot submit a blank comment.

It all boils down to whether or not it is clear to users that the central node cannot be deleted. Personally, I find it rather clear why you cannot delete the central node in XMind, but that's just me (and the fact that every mindmap starts with that central node).


I woulf just make it undeletablr. So wehen you select everything and delete it everything is gone except this one soecial node.

You should also make the node use a special icon or color.

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