Survey of the Global Fortran Community

This dataset contains the survey responses and associated analysis artefacts collected for the study “What do we really know about Fortran?”. The study investigates the current state of Fortran codebases in scientific and engineering computing, with a particular focus on the long-term sustainability challenges faced by the practitioners who maintain them. The survey was conducted in 2025–2026 and gathered responses from 150 participants across 25 countries. Respondents were asked to focus on a single Fortran codebase of their choosing, and to answer 39 questions spanning 8 thematic sections: codebase characteristics (size, age, Fortran standard versions, licensing), technical dependencies and HPC requirements, documentation practices, legacy status, key challenges, potential improvements, organisational context, scientific domain, and respondent demographics. The codebases described by respondents support work in a wide range of safety- and mission-critical domains, including numerical weather prediction, nuclear physics, plasma physics and fusion energy research, geophysics, computational chemistry, atmospheric science, and national defence. Codebase sizes range from under 1,000 lines of code to more than 5 million lines. The majority of respondents (82%) hold a PhD or higher qualification, 32% are over 55 years of age, and 26% are the sole maintainer of their codebase — together these figures underscore the workforce sustainability risks that motivated the study. The dataset is provided to support the reproducibility of the analyses reported in the manuscript and to enable further research on the long-term sustainability of scientific software. High resolution images from the published paper are also included for convenience.