The right time of form validation has been discussed already several times here, here and here, but recently I noticed a few times implementations which are using delayed validation. Means you get your validation as soon as you are stop typing, after a short delay. It seems superior to the onKeyPress validation, but is it superior to onBlur? In general?

Example of delayed form validation (of course: in case of an error, the error should get hidden immediately here and the delay seems to be too short)

In the alist apart study they've used partly the delayed method, but only for username and password, which worked quite good for them.

  • 2
    Your example of delayed form validation already shows why it's a bad practise; I was trying to input my email, and the moment my fingers left the keyboard to make a @ symbol, I was hit with a "Please enter a valid email address". Yes I know website, I was not done yet... This is why out of focus is preferred. – Wanda Sep 8 '17 at 10:02
up vote 3 down vote accepted

It is very important to remember that validation should take place after the input is complete

Validation that takes place while typing (even with slight delay) is really annoying because it prompts the user about mistakes that he/she hasn't yet made.

The best time to trigger validation is:

  • on focusOut
  • on press of the Submit button
  • (in case of unavoidable scenarios like picking username) on click of Validate button

...only for username and password, which worked quite good for them.

Username makes sense because sometimes even the user isn't sure about what to pick as it needs to be unique.

For password, however, the method of mentioning the rules and ticking them off as the user enters is one of most intuitive methods I have come across. See here

There are a number of circumstances when Delayed on KeyPress can't be effective:

  1. Everyone doesn't have the same typing speed.
  2. People are not robots, they take pauses.

On other hand, out of focus has been our friend for many years. I believe >50% web users are familiar with this.

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