EESSI Versions

EESSI is organized in different dated versions. Each EESSI version contains a version of the compatibility layer and its' own set of software applications. In addition, a particular EESSI version will target a different set of common toolchains to build software with. As an example, the first EESSI version was released in June 2023 and is named 2023.06. This version's compatibility layer is based on a particular "version¹" of Gentoo Prefix and the software layer contains software built using the foss/2022b, foss/2023a, and foss/2023b software toolchains as defined in EasyBuild.

The vast majority of changes are fully transparent to users. Apart from selecting a newer version when starting up EESSI, and accessing an update collection of software, the functionality remains the same, with little to no extra effort needed to use a new version compared to and older one.

Going forward, EESSI aims to have yearly version releases, which will target a more recent set of toolchains and an updated set of compatibility layer components.

Current EESSI versions

EESSI Version	Included toolchains	Software list
2023.06 (default)	foss/2022b foss/2023a foss/2023b	2023.06
2025.06	foss/2024a foss/2025a	Coming Soon

The current default EESSI version is 2023.06. Version 2025.06 is already fully available and will be made the default soon, once it contains more software.

Switching between EESSI versions

• The simplest way to load a specific EESSI version or to switch between them, is to load the appropriate environment module. To access version 2023.06 one can simply do module load EESSI/2023.06 and switching to the 2025.06 version is just as easy with: module load EESSI/2025.06. This will automatically set up the environment and avoid conflicts between versions.

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1. technically: a specific commit, since Gentoo Prefix doesn't have versioned releases. ↩