Non-destructive testing (NDT) is an analysis technique used in scientific fields to determine the state or function of a system by comparing a known input with a measured output, without the use of invasive approaches like disassembly or failure testing.

Because NDT does not require the disabling or sacrifice of the system of interest, it is a highly-valuable technique that saves both money and time in product evaluation, troubleshooting and research.

Common NDT methods include acoustic testing, liquid penetrate testing and radiographic testing. NDT can be used with any isolated input / output system and is a commonly-used tool in forensic engineering, mechanical engineering, electrical engineering, civil engineering, systems engineering and medicine.