Customer journeys
An error message should tell the person what can happen next
Translate a failed operation into a useful business explanation without exposing private diagnostics.
A customer tries to change a request and sees “operation failed.” They cannot tell whether the change was rejected, partly saved or still being processed. The next action matters more to them than the internal name of the error.
Describe what is known
For a fictional Estonia-connected service, distinguish a field that needs correction from an unavailable system and a request that needs staff review. State whether the original information remains in place and whether the customer should retry or contact someone.
Do not promise that nothing happened unless the system can establish it. A repeated action can create confusion when the first attempt may already have reached another tool.
Keep the explanation appropriate to the audience
W3C's notification guidance recommends understandable feedback and practical correction instructions. A customer-facing message should use that principle, while authorised support can receive suitable diagnostic context through a separate route.
Avoid copying credentials, private record contents or internal infrastructure details into the public error. More technical detail does not necessarily help the person finish the task.
Test recovery, not only rejection
Create an approved demonstration error, correct the input and continue. Check whether useful non-sensitive details are preserved and whether the person reaches the intended result without starting from the beginning. Include a case that genuinely requires staff action.
Ask a colleague unfamiliar with the implementation to explain what the message means. If they cannot tell what to do, refine it before treating the error handling as finished.
A usability and accessibility improvement can focus on this recovery path. The deliverable should include the actual corrected journey and any limits, not merely a new message string.
Further reading: W3C guidance on understandable error feedback.