Fortran Compilers

There are several free compilers available or up-coming for Unix-like operating systems that support modern Fortran language standards:

Front-end for LLVM, with limited support of the Fortran 2003 and 2008 language standards. Based on source code of PGI.
LLVM front-end for Fortran 2018 in development, contributed by NVIDIA.
GNU Fortran (gfortran)
Modern Fortran compiler, part of the GNU Compiler Collection and successor of g77.
Intel oneAPI Fortran
Intel’s LLVM-based Fortran, C, and C++ compilers for Windows, Linux, and macOS (freeware).
IBM XL Fortran
Proprietary no-charge full-function Community Edition of IBM’s Fortran compiler for Linux.
A Fortran 2018 REPL-like front-end for LLVM, in pre-alpha stage.

GNU Fortran is a fork of G95, a discontinued Fortran 95 compiler that has been removed from the FreeBSD ports collection due to deprecated dependencies that are required for building. Flang in an older front-end for LLVM, missing most features of Fortran 2008 and 2018.

Fortran compilers are available for many platforms. Most of them target Microsoft Windows and/or Linux, but do not produce native binaries for FreeBSD and other Unix systems, like Intel Fortran, PGI Community Edition, or the abandoned Open64.

Some historic compilers for FORTRAN 77 are open-source as well:

Proprietary compilers targeting CP/M, DOS (fig. 1), and Microsoft Windows can be downloaded from various web sites dedicated to historic software, like or

Microsoft FORTRAN Compiler for DOS
Fig. 1: Box of Microsoft FORTRAN Compiler for DOS

Online Compilers

There are services that provide online access to Fortran compilers, to build and run Fortran programs through the web browser, like:

You may want to try some of the examples in the next sections by using an online compiler.

Modern Fortran on FreeBSD

Using FreeBSD as a programming environment for modern Fortran currently limits the list of available compilers to GNU Fortran and Flang, as Flang/F18 is still in early stage and LFortran is just a prototype. All four can be installed from ports or by using the FreeBSD package manager. The Intel Fortran compiler for FreeBSD was removed from the ports collection in 2010.