Fourier-transform infrared (FTIR) spectroscopy is a technique used to obtain an infrared spectrum of absorption or emission of a solid, liquid or gas.

It is a technique used to examine chemical composition using the infrared (IR) part of the electromagnetic spectrum.

FTIR spectroscopy flashes a sample with a series of broadband light of varying IR wavelengths. The resulting collection of spectra are then interpreted using the Fourier transform algorithm to indicate which parts of the spectrum were absorbed, and therefore, the chemical composition of the sample.