For the Error Prevention heuristic, it states, “Good error messages are important, but the best designs carefully prevent problems from occurring in the first place. Either eliminate error-prone conditions, or check for them and present users with a confirmation option before they commit to the action.”
There are two types of mistakes made by users, slips and mistakes.
Slips are when the user intended to perform one action, but accidentally selects another. One example is when they click the wrong button on a page layout. Let’s say the Delete button is right next to the Edit button. They meant to click Edit, but actually clicked Delete.
This type of error can be addressed by either separating the two buttons, and/or adding a confirmation message before performing the actual delete.
Another way to prevent slips is to build guardrails. For example, if your system needs a start date and end date from the user, you can ensure that the start date is always earlier, or the same as, the end date. You can also include good defaults.
Mistakes are when the user doesn’t fully understand the context or don’t have enough information. They believe they are following the correct path, but end up with an error. This often happens when their existing mental model of how something works doesn’t match the user experience.
Keeping your design consistent and using help text can help avoid mistakes. Validation rules and useful error messages can be useful to guide the user to recover from mistakes.
The takeaway
It’s important to communicate errors to users gracefully, actionably, and clearly. However, it’s even better to prevent users from making errors in the first place.