Skip to main content

LEOS 3.3.0. Switch to the latest release

Published on: 02/02/2023 Last update: 26/04/2024

About LEOS


LEOS (Legislation Editing Open Software) is a software designed to address the need of the public administration and European Institutions to generate draft legislation in a legal XML format. It was created under  ISA Programme - ISA Action 1.13. LEOS - Legislation Editing Open Software and it continued to evolved under ISA2 Action 2016.38 Legislation Interoperability Tools - LegIT.  The LEOS journey continues under Digital Europe Programme (DIGITAL).


LEOS has been created to addresses the modernisation and digital transformation of the drafting and revising of legislation in EU Institutions, EU agencies and bodies and Member States. The aim is to:

  • Improve the quality of legislation.
  • Increase the efficiency of the legislative process across the Union.
  • Facilitate interoperability and seamless cooperation between the different actors in the legislative process in and between EU Institutions and Member States.
  • Improve transparency and accessibility and thus effectiveness of law.
  • Explore and pilot the use of innovative technologies such as Artificial Intelligence.

It is based on the Akoma Ntoso XML format an OASIS LegalDocML standard (in particular, it supports the AKN4EU interinstitutional instantiation subschema of Akoma Ntoso) that facilitates interoperability between EU institutions and Member States


The code is available for free under EUPL licence (version 1.2 or – as soon they will be approved by the European Commission - subsequent versions of the EUPL (the "Licence")) on, and the development team paid attention to organise the code in a structured way to ease its reusability (modules, plugins…).  

For more information on the EUPL licence, please visit this link


What’s new?

The main differences compared to the previous version are:

Technical Improvements

  • Services layer refactored in a more generic and extensible fashion;
  • Projects structure revisited to ease the creation of tailor made solutions based on LEOS;


Integration Services

  • New service for creating special user and special entities upon identified need;
  • New REST service for retrieving all collaborators from a proposal;


Revision improvements

  • New autonumbering feature enabling a revision proposal numbering to be renumbered as drafting on Legal Act;
  • New autonumbering feature enabling a revision proposal numbering to be renumbered as drafting on Annexes;


Statement of Council Reasons

  • Enable user to set any version as base for comparison on Statement of Council Reasons documents;


Bug Fixes

  • Drafting
    • Improved pre-finalization metadata display handling;
    • Fork&Merge:
      • Improved handling of eeaRelevance merging in cover page;
  • Revision 
    • Improved handling of point structure when using backspace;
    • Annexes with origin in revision version were not showing new text as bold;
    • Fixed double spaces present on Coreper/Council AKN template;


Get in touch

We are envisaging to create an open source community on software for legislation drafting, in order to share best practices, experiences, expertise, and why not code!!

To join our open source community on please go here.

If you would just like to share with us some observations on our work, please contact us at:

Last update: 02/02/2023

LEOS 3.3.0

European Union Public Licence, Version 1.2 or later (EUPL)