Let's say my application has two input fields. Here is the situation:

  • When starting the application, both fields are empty.
  • When entering a value into one of the fields, it will be parsed to a number (Only after the value changes!).
  • If the parse succeeds for both fields, a sum will be displayed.
  • If the parse does not succeed, the field will change to display a red border, the sum will disappear. This also includes empty values.

The problem: At the beginning, the empty fields do not indicate an error, but when entering and then deleting something (The field returning to the old state) an error will be indicated.

My question: When should an error be displayed and how should an initial and a non-inital empty field be treated by the application?

  • If both fields are empty: return nothing, regardless of initial state or not. If one is empty and one is filled, error.
    – Alan
    Feb 1, 2018 at 13:26

1 Answer 1


Everything is correct, as empty field is not a number which is expected. You should also indicate an error if input is of text type. In addition to that, your UX would benefit from explaining the error.

Here is an example from Semantic UI:

enter image description here

  • My question mainly focused on the fact that the fields would not be prefilled, but still shouldn't display an error. This, in combination with a dynamic event system instead of a "submit"-button complicates the matter. Feb 1, 2018 at 12:52
  • The error notification is just for what it is - an error. If there is no error, you should not indicate one. So first you should work out what is an error and what is not an error yet. Feb 2, 2018 at 10:30

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