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Error prevention: how to prevent slip-type errors

Sheza Naveed

Preventing errors is the 5th usability heuristic. However, these errors are not user errors; rather, they are design errors that occur when the design should be of the sort that does not allow the user to commit errors or at least gives a warning before the user is about to commit an error.

Error prevention can be done by:

  • eliminating error-prone conditions

  • presenting users with a warning message that informs them of the consequences if they proceed, and a confirmation option if they are about to commit an error.

There are two types of errors:

  • Slips - unconscious errors caused by the user’s inattention.

  • Mistakes - conscious errors caused by a mismatch between the design and the user’s mental model.

Slips are often performed by expert users who feel that they have mastered the tasks and do not need to pay full attention. Slips occur when users are familiar with the task they want to perform, but they accidentally perform the wrong step.


Slips can be prevented by guiding users to stay on the right path and reducing the chances of slipping. The following guidelines can help to prevent or reduce the chances of slips:

  • Helpful constraints - in cases where providing freedom to the users significantly increases the chances of error, it is better to constrain the user choices to a certain extent (e.g., if the amount text field only requires numbers to be entered, giving the option to enter letters will do no good; so, it is better to restrict the user and not allow them to input anything other than numbers). As shown below, the interface below only allows for dates to be added; thus, leaving less room for slips.
Source: Airbnb
  • Suggestions - meaningful suggestions can prevent slips from happening. For example, users are bound to make typos, so giving them suggestions to choose from can prevent slips.
Source: Huewei website
  • Defaults - providing helpful defaults can prevent slips, especially when repetitive actions need to be performed. Good defaults fit real-world goals (e.g. typical options such as tomorrow, next week, etc.) This is shown below:
Source: NN group
  • Forgiving formatting - some text fields require users to input in a very specific format with strict spaces. However, making these options more flexible reduces the chances of slips. For example, Uber adds the required spaces itself when required, as shown below:
Source: NN group


Slips are common errors that occur when the user is not giving their full attention. It is essential to prevent slips as it will reduce the burden on users and make their experience smoother.




Sheza Naveed
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