What Is UAT? User Acceptance Testing, Explained

UAT (user acceptance testing) is the final check before software goes live, where the people who will actually use it confirm it does what they need. Real users run real tasks, and their sign-off decides whether it ships.

UAT comes after the developers' own testing. Once the code passes system and integration testing, the software goes to the people it was built for. The testers are usually a handful of the staff who will live in the tool every day, not the IT team. They don't test whether the code runs. They test whether it fits the way they work.

That difference matters. A developer confirms the invoice screen saves without error. A UAT tester, who is an actual accounts clerk, notices the screen makes them enter the tax code twice, which no requirement document ever mentioned. Those are the problems UAT catches: the gap between "works as specified" and "works in real life".

An example from our world: a dispatch tool for a freight forwarder is done. Before launch, two dispatchers spend a few days booking real shipments through it. They flag that the pickup time defaults to the wrong timezone. We fix it, they re-check, and only then does the tool go live.

Why it matters for custom software

UAT is the step that protects a fixed-scope delivery. Real users sign off before launch, so the software matches the business rather than a spec written weeks earlier. That honest final check is built into how we work, and it's why our short builds hold up once they're in daily use.