Error messages are UX moments. A bad error frustrates. A good error guides recovery.
The Formula
- What happened — "Your password must be at least 8 characters"
- Why — "Passwords shorter than 8 characters are easy to guess"
- How to fix — "Add more characters to continue"
Tone Matters
Never blame the user. "Invalid input" sounds accusatory. "Please enter a valid email address" is helpful.
Write error messages as if you're a helpful colleague, not a strict validator.