Red Hat Enterprise Linux (RHEL) is a commercial open-source[1][2][3] Linux distribution[10][11] developed by Red Hat for the commercial market. Red Hat Enterprise Linux is released in server versions for x86-64, Power ISA, ARM64, and IBM Z and a desktop version for x86-64. Fedora Linux and CentOS Stream serve as its upstream sources. All of Red Hat's official support and training, together with the Red Hat Certification Program, focuses on the Red Hat Enterprise Linux platform.
The first version of Red Hat Enterprise Linux to bear the name originally came onto the market as "Red Hat Linux Advanced Server". In 2003, Red Hat rebranded Red Hat Linux Advanced Server to "Red Hat Enterprise Linux AS" and added two more variants, Red Hat Enterprise Linux ES and Red Hat Enterprise Linux WS.[12]
Red Hat previously used strict trademark rules to restrict free re-distribution of their officially supported versions of Red Hat Enterprise Linux[13] but still freely provided its source code. Third-party derivatives were able to be built and redistributed by stripping away non-free components like Red Hat's trademarks. Examples include community-supported distributions like Rocky Linux and AlmaLinux, and commercial forks like Oracle Linux. In 2023, Red Hat decided to stop making the source code of Red Hat Enterprise Linux available to the public. The code is still available to Red Hat customers, as well as developers using free accounts, though under conditions that forbid redistribution of the source code.[11]
Red Hat Enterprise Linux Server subscription is available at no cost for development purposes.[14] Developers need to register for the Red Hat Developer Program and agree to license terms forbidding production use and redistribution of the source code.[11] This free developer subscription was announced on March 31, 2016.
There are also "Academic" editions of the Desktop and Server variants.[15] They are offered to schools and students, are less expensive, and are provided with Red Hat technical support as an optional extra. Web support based on the number of customer contacts can be purchased separately.
It is often assumed the branding ES, AS, and WS stand for "Entry-level Server", "Advanced Server" and "Work Station", respectively. The reason for this is that the ES product is indeed the company's base enterprise server product, while AS is the more advanced product. However, nowhere on its site or in its literature does Red Hat say what AS, ES, and WS stand for.