Error messages are not a place to demonstrate your literary skills. Often, users are already on edge when they encounter an error. An error message that is lengthy, confusing, or unhelpful is likely to push them to the point of never wanting to come back to your product.

A clear and concise error message is one that:

• Uses as few words as possible while making sure that the meaning of the message is intact
• Is easy to understand at a glance
• Does not use technical jargon or high-level language
• Tells the user what to do next

Keeping it short and explicit achieves the dual objective of grabbing your users’ attention while adopting a tone that is not domineering or high-handed.