Visual inspection or Visual testing (VT) is  a non-destructive testing technique that provides a means of detecting and examining a variety of surface flaws, such as corrosion, contaminations, surface finish, and surface discontinuities on joints (for example, welds, seals, solder connections, and adhesive bonds).

Visual inspection is also the most widely used method for detecting and examining surface cracks, which are particularly important because of their relationship to structual failure mechanisms.

Picture 1: Visual testing by magnifying glass.

Picture 2: Visual testing by Video scope.