A TDMS file is a data file saved in the National Instruments (NI) Technical Data Management Streaming (TDMS) format. It contains simulation or measurement data recorded by National Instruments software, such as LabVIEW and DIAdem. TDMS files also store descriptive information, which includes the procedure, test fixture, sensor information, and author.

The TDMS format was developed by National Instruments to make it easier for scientists and engineers to store large amounts of data recorded from tests and simulations. The TDMS format is supported by a variety of National Instruments programs, including LabVIEW and DIAdem. It is also supported by MathWorks MATLAB and OpenOffice Calc. TDMS_INDEX files are created automatically with TDMS files. The index files contain information about the associated TDMS file that is referenced by the application opening the TDMS file. This allows TDMS files that store large data sets to be opened quicker.