What is a .f90 file?
Fortran Source File · Code and data · IBM (John Backus); ISO committee · 1957 (Fortran); 1991 (Fortran 90)
An .f90 file is Fortran source code in free-form layout, introduced with Fortran 90. Fortran is the oldest language still in serious use and remains a workhorse of scientific and numerical computing.
What is a .f90 file used for?
Fortran (Formula Translation) appeared in 1957 and still dominates weather models, physics simulations and the numerical libraries under many Python packages, because compilers make its array math extremely fast.
The extension marks the layout: .f and .for hold old fixed-column code, while .f90 and .f95 hold modern free-form code (of any standard up to the current one). All are plain text.
What opens a .f90 file?
The .f90 format opens in the following apps, grouped by operating system. If one app does not work, try another from the same list.
Windows
- VS Code (Modern Fortran)
- gfortran (to compile)
- any text editor
macOS
- VS Code (Modern Fortran)
- gfortran
- any text editor
Linux
- VS Code (Modern Fortran)
- gfortran
- any text editor
Open a .f90 file step by step
- Confirm the file really is a .f90. Drop it into the WhatFileType identifier, which reads its signature in your browser without uploading anything.
- On Windows, open it with VS Code (Modern Fortran) or gfortran (to compile).
- On Mac, use VS Code (Modern Fortran) or gfortran.
- On Linux, try VS Code (Modern Fortran) or gfortran.
- Still stuck? Convert the .f90 to exe (compiled), which opens more widely.
Why can't I open my .f90 file?
Almost always because no installed app understands Fortran. Install one of the apps above, or convert the file to a format your existing software already reads. If double-clicking opens the wrong program instead of nothing at all, the file association is set to the wrong app rather than the file being broken.
The other possibility is that the file is not really a .f90 at all. Drop it into the file identifier to check it by its bytes instead of its name. Nothing is uploaded.
How to convert a .f90 file
You can convert a .f90 file to exe (compiled) using a conversion tool or the export menu of an app that opens it.
Fortran has no fixed magic number, so there is no signature table on this page. Its bytes alone do not prove the format: identification relies on the extension, the structure of the content and the program that created it. The magic-numbers reference lists the formats that do carry one.
Frequently asked questions
What is a .f90 file?
An .f90 file is Fortran source code in free-form layout, introduced with Fortran 90. Fortran is the oldest language still in serious use and remains a workhorse of scientific and numerical computing.
How do I run an .f90 file?
Compile it with a Fortran compiler, for example gfortran file.f90 -o program, then run the resulting executable. Intel's ifx is a common alternative compiler.
What is the difference between .f and .f90?
Layout. .f (and .for) files use the old fixed-column format from the punch-card era; .f90 and .f95 files use the free-form layout that modern Fortran allows.
Is Fortran still used?
Very much. Weather forecasting, computational physics and HPC codebases run on Fortran, and libraries like LAPACK sit underneath tools such as NumPy.
Related formats
Sources
Details on this page were checked against authoritative references. How sources are ranked and what is deliberately left out is set out in the methodology.