What is user acceptance testing (UAT)?

User acceptance testing (UAT) is validation by business users or customers that the system meets agreed requirements before go-live. Participants run realistic scenarios in a staging or pilot environment using production-like data and workflows. UAT focuses on “fit for purpose” and business rules, not developer-level edge cases already covered in earlier cycles. Sign-off from UAT often gates release in enterprise and compliance-driven products. It differs from QA regression: QA proves quality; UAT proves the right product was built. Clear acceptance criteria and traceability to requirements reduce last-minute surprises. Poor UAT planning is a common cause of production defects that “passed QA.”