1 Boston University, Neurophotonics Center, Department of Biomedical Engineering, Boston, Massachusetts, United States.
2 NIRx Medical Technologies, Berlin, Germany.
3 Artinis Medical Systems B.V., Elst, The Netherlands.
4 Gowerlabs, London, United Kingdom.
5 University of Nottingham, Nottingham, United Kingdom.
6 University College London, London, United Kingdom.
7 Radboud University, Donders Institute for Brain, Cognition and Behaviour, Nijmegen, The Netherlands.
8 Karolinska Institutet, NatMEG, Stockholm, Sweden.
9 Maastricht University, Maastricht, The Netherlands.
10 Brain Innovation B.V., Maastricht, The Netherlands.
11 Concordia University, Montreal, Quebec, Canada.
12 Kernel, Los Angeles, California, United States.
13 OBELAB, Seoul, Republic

Significance: Functional near-infrared spectroscopy (fNIRS) is a popular neuroimaging technique with proliferating hardware platforms, analysis approaches, and software tools. There has not been a standardized file format for storing fNIRS data, which has hindered the sharing of data as well as the adoption and development of software tools.

Aim: We endeavored to design a file format to facilitate the analysis and sharing of fNIRS data that is flexible enough to meet the community's needs and sufficiently defined to be implemented consistently across various hardware and software platforms.

Approach: The shared NIRS format (SNIRF) specification was developed in consultation with the academic and commercial fNIRS community and the Society for functional Near Infrared Spectroscopy.

Results: The SNIRF specification defines a format for fNIRS data acquired using continuous wave, frequency domain, time domain, and diffuse correlation spectroscopy devices.

Conclusions: We present the SNIRF along with validation software and example datasets. Support for reading and writing SNIRF data has been implemented by major hardware and software platforms, and the format has found widespread use in the fNIRS community.