This study presents a comprehensive Fourier-transform infrared (FTIR) spectroscopy characterization of 12 typical carbide and carbonitride MXenes, including Ti3CT2, Nb2CT2, Mo2CT2, V3CT2, Ti3C2Tx, Ti3CNTx, Mo2TiC2Tx, Mo2Ti2C3Tx, Nb4C3Tx, V4C3Tx, Ta4C3Tx, and Mo4VC2Tx. The research aims to establish an FTIR spectral library for the reliable identification and analysis of MXenes. The study provides detailed instructions for sample preparation, data collection, and interpretation of FTIR spectra, including background correction and spectrum smoothing to enhance peak clarity. Density functional theory (DFT) calculations were used to assign characteristic FTIR peaks and analyze vibration modes. The work highlights the influence of MXene composition, structure, and surface terminations on their FTIR fingerprints, providing valuable insights for the 2D material community. The study also discusses the correlation between FTIR peak positions and chemical composition, as well as the impact of layer number on MXene structures. Overall, this research establishes a robust foundation for the use of FTIR spectroscopy in the analysis of MXenes.This study presents a comprehensive Fourier-transform infrared (FTIR) spectroscopy characterization of 12 typical carbide and carbonitride MXenes, including Ti3CT2, Nb2CT2, Mo2CT2, V3CT2, Ti3C2Tx, Ti3CNTx, Mo2TiC2Tx, Mo2Ti2C3Tx, Nb4C3Tx, V4C3Tx, Ta4C3Tx, and Mo4VC2Tx. The research aims to establish an FTIR spectral library for the reliable identification and analysis of MXenes. The study provides detailed instructions for sample preparation, data collection, and interpretation of FTIR spectra, including background correction and spectrum smoothing to enhance peak clarity. Density functional theory (DFT) calculations were used to assign characteristic FTIR peaks and analyze vibration modes. The work highlights the influence of MXene composition, structure, and surface terminations on their FTIR fingerprints, providing valuable insights for the 2D material community. The study also discusses the correlation between FTIR peak positions and chemical composition, as well as the impact of layer number on MXene structures. Overall, this research establishes a robust foundation for the use of FTIR spectroscopy in the analysis of MXenes.