Summary: Jakob Nielsen’s usability heuristic 9: Help Users Recognize, Diagnose, and Recover from Errors. Write error messages in plain language, provide precise problem identification, and offer actionable solutions to help users quickly overcome the issue.
This article is about Jakob Nielsen’s Usability Heuristic number 9: “Help Users Recognize, Diagnose, & Recover from Errors.” See also the list of all 10 usability heuristics.
Jakob Nielsen’s ninth usability heuristic emphasizes that effective user interfaces must help users recognize, diagnose, and recover from errors. At its core, this principle is about empathy: when users encounter problems, they should not feel lost, frustrated, or blamed. Instead, interfaces should guide them toward resolution with clarity and actionable support.
This heuristic urges designers to craft error messages in plain language, avoiding technical jargon, and to pair problems with actionable solutions. By doing so, users can quickly recognize an issue, diagnose its cause, and recover without unnecessary effort — reducing cognitive load and fostering trust in the system.
Think of error messages as GPS rerouting in a vehicle navigation system: they should tell you where you went wrong, where you are now, and how to get back on track.
Error situations are disruptive and frustrating for users. People will abandon a website if something goes wrong and they don’t know how to fix it. Good error messages help users and save business. (Leonardo)
Why Is This Heuristic Important?
Reduces frustration: Poorly communicated errors alienate users, leading to abandonment or dissatisfaction.
Saves time: Clear instructions help users resolve issues quickly, improving efficiency.
Builds trust: Transparent communication fosters confidence in the product or service.
For UX designers, mastering this heuristic is critical. Errors are inevitable in any system, but how they’re handled defines the quality of the user experience.
A good error message can be a teachable moment and advance users’ understanding of the system, helping them to construct an accurate mental model.
Better error messages lead to better user experience. (Napkin)
Guidelines for Designing Error Messages that Comply with Heuristic 9
To comply with Nielsen’s ninth usability heuristic, follow these design guidelines when writing error messages:
Use Plain Language
Avoid technical jargon, codes, or vague terms (e.g., “Error 502” or “Operation failed”).
Example: Replace “Invalid input” with “Password must contain at least one number.”
Diagnose and Direct
Clearly identify what went wrong and where.
Example: “The email ‘user@example’ is already registered” instead of “Registration error.”
Provide Actionable Solutions
Offer step-by-step fixes, such as buttons, links, or examples.
Example: “File too large? Compress it or try a smaller file (max 10MB).”
Design for Visibility and Tone
Use color, icons, or highlighting to ensure they’re noticeable without overwhelming or alarming users (e.g., yellow warnings instead of red alerts).
Avoid accusatory language (e.g., “You entered the wrong password” → “Password incorrect”).
Empower Recovery
Provide buttons, links, or shortcuts to help users act immediately (e.g., “Retry” or “Contact Support”).
Five steps to emphasize when designing error messages. (Napkin)
Digital Examples: Good vs. Bad Error Messages
Bad Example: Cryptic and unhelpful error message: “Invalid input. Please try again.”
This message violates the heuristic in the following ways:
It fails to explain what was invalid or how to fix it.
Users are left guessing whether their email format, password length, or another field caused the error.
Rewritten for compliance with the heuristic: “The password must be at least 8 characters and include a number. Please update your password and try again.” This rewrite incorporates these improvements:
This specifies the problem (password length/format).
The copy helps users correct the problem by explaining the requirements
The message provides directions for the next step to solve the problem.
Good Example: Clear and supportive error message:
“Your card was declined. Possible reasons:
Insufficient funds
Incorrect expiration date
Please check your details or try another payment method.”
This message complies with the heuristic as follows:
Diagnoses potential causes.
Provides specific, actionable steps to resolve the issue.
(The message is also scannable, using a bulleted list, thus furthermore complying with my guidelines for writing for the web.)
Physical World Examples: Error Messages Beyond Screens
Error communication isn’t limited to digital interfaces. Let’s examine some real-world examples:
Bad Physical Example: Vending machine error message: “Out of Order.” This message violates the heuristic in the following ways:
Fails to explain why the machine isn’t working (e.g., no change, mechanical issue).
Offers no guidance (e.g., “Try another machine” or “Card payments only”).
Rewritten for compliance with the heuristic: “Temporarily unable to accept cash. Please use card payment or visit Machine #2.” This rewrite incorporates these improvements:
Explains the specific issue (cash mechanism broken).
Provides alternatives to resolve the problem.
Good Physical Example: Elevator error message: “Door stuck? Press the emergency button and wait for assistance.”
This message complies with the heuristic as follows:
Diagnoses the problem (“door stuck”).
Offers a clear solution (press the emergency button).
Conclusion: Designing for Empathy and Efficiency
Jakob Nielsen’s ninth heuristic reminds us that errors are opportunities to build trust. Whether in digital interfaces or physical systems, users deserve clear, respectful guidance when things go wrong. By prioritizing plain language, specificity, and actionable solutions, designers can transform frustrating roadblocks into moments of empowerment.
Interfaces should guide users through errors by clearly communicating what went wrong, why it happened, and how to fix it. Errors are inevitable in user interactions, but poorly handled errors can lead to frustration, confusion, or task abandonment.
At first, the heuristic may seem limited to UX writing. After all, it’s about UI copy. But providing helpful error messages often requires architectural changes to the software. Specificity and one-click access to problem solutions may only be possible if lower levels of the system can bubble up the actual problem to the UI level so that it can be communicated to the user.
Even the best error message will rarely make users this happy. But good error messages do create a better user experience. (Midjourney)
For UX designers, practicing heuristic evaluation with this lens will sharpen your ability to critique and improve interfaces — ensuring they serve users not just in ideal scenarios, but in moments of confusion too. Remember: good design doesn’t just prevent errors; it makes recovery effortless.
Clear alerts. Plain language. Constructive fixes. No jargon. Swift recovery. What’s not to like about these guidelines?
Or, as a metaphor, Be a digital doctor: diagnose errors (symptoms), explain causes (illness), and prescribe fixes (cure). User wellness matters.
Haikus About Usability Heuristic Number 9
Codes speak in riddles, Clarity breaks through the noise— A fix takes one step.
Mistakes bloom in red, Steps to mend the break, unveiled— No fear in the fall.
Mistakes whisper fear, Kind words map the route back home— No dead ends remain.
Video Explainer
Watch avatar explainer of Heuristic 9 (You Tube, 3 min. video).