Error Prevention
Prevent errors before they happen by removing risky choices, setting useful limits, and checking high-impact actions.
A good safeguard keeps the wrong path from looking available.
Someone selects a return date before their departure date. The form could wait until checkout to complain, or the calendar could make the invalid choice unavailable. The second option keeps the error from becoming a problem.
Origin
Jakob Nielsen included Error Prevention in his 1994 usability heuristics. In 2015, Page Laubheimer expanded the practical guidance for digital products through constraints, suggestions, good defaults, and forgiving input formats.
Start with the errors that could cause the most harm or cost. A small inconvenience and an irreversible action should not receive the same level of protection.
Use constraints when the rules are clear. Disable impossible dates, prevent invalid combinations, and remove choices that cannot lead to a valid result.
Offer sensible defaults and suggestions. Guide people toward a likely answer while keeping the final choice in their hands.
Before an irreversible action, show what will happen and ask for confirmation. For ordinary input, validate early so people can correct it while the context is still clear.
Digital systems
Southwest Date Picker
Southwest's date picker required people to choose a departure date before a return date. By controlling the order of selection, it prevented an impossible date range before submission.
Physical signals
Highway Guardrails
Guardrails on curvy mountain roads help stop vehicles from leaving the road. The physical boundary limits how far a driving error can go before it causes greater harm.
If the interface accepts an invalid choice and complains later, the user must find the problem, understand it, and try again. The product turns a preventable issue into recovery work.
Remove impossible options, guide input with sensible defaults, and validate while people work. For high-impact actions, show the consequence clearly before they commit.