User acceptance testing (UAT)
Also called: UAT, acceptance testing, business acceptance
User acceptance testing is the step where the people who asked for a change decide whether to accept it as built, knowing what is known about it.
User acceptance testing (UAT) answers one question: will the business accept this release as it stands? It comes after functional testing. Functional testing checks that the product behaves as specified, and the tester judges the result. In UAT the business owner judges, because only they can accept risk on behalf of the business.
UAT goes wrong when it is treated as a demo or a second round of bug hunting. The usual signs are a late invite, a checklist nobody in the room has read, and a sign-off that does not say what was exercised.
I run UAT as a decision. Acceptance criteria and the journeys in scope are agreed before anyone is invited, each observation is recorded against a criterion with an owner, and the output is a short pack that says what passed, what is deferred with a named risk, and what blocks the release.
Template: UAT summary and sign-off template