Preface by the BENEVOL 2022 Organizers BENEVOL 2022, the 21st Belgium-Netherlands Software Evolution Workshop was held in Mons, Belgium on September 12-13 2022. Past editions of BENEVOL saw presentations on mining software repositories, source code analysis and manipulation, software testing, bugs and socio-technical aspects in software engineering. This year, the papers accepted at BENEVOL evolved around software ecosystems, mining software repositories, software testing, open source software, development, design and databases. More information about BENEVOL 2022 can be found at: https://benevol2022.github.io/ BENEVOL 2022 invited submissions of technical papers and presentation abstracts. Technical papers concern novel results, possibly in the early stages of research and they are included in the proceedings. On the other hand, presentation abstracts report research results that are either already published or are novel results, so they are not included in the proceedings. BENEVOL 2022 received 37 submissions in total; 22 presentation abstracts and 15 technical papers. All papers were reviewed by three referees. Ten technical papers were accepted (out of 15 submissions) and 27 submissions were accepted as presentation abstracts (including the five rejected technical papers). Thus, the proceedings include 10 technical papers; 7 of them are regular papers and 3 are short papers. Two keynote speeches took place at BENEVOL 2022. Michail Papadakis (senior research scientist at the University of Luxemburg, Luxemburg) gave the keynote speech “Applying Mutation Testing in Evolving Systems”, while Gregorio Robles (Professor at the Universidad Rey Juan Carlos, Spain) gave the second keynote “Let’s talk about bugs!”. We would like to thank the program committee, the members of the organizing committee and the student volunteers who contributed to have a very interactive BENEVOL 2022. September 2022 BENEVOL 2022 PC Chairs Mairieli Wessel Eleni Constantinou Copyright 2022 for this preface by its authors. Use permitted under Creative Commons License Attribution 4.0 International (CC BY 4.0) Organizing Team Tom Mens, University of Mons (UMons), Belgium (General chair) Mairieli Wessel, Radboud University (RU), The Netherlands (Program co-chair) Eleni Constantinou, Eindhoven University of Technology (TU/e), The Netherlands (Program co-chair) Alexandre Decan, University of Mons (UMons), Belgium (Local co-organizer) Pooya Rostami Mazrae, University of Mons (UMons), Belgium (Publicity co-chair) Natarajan Chidambaram, University of Mons (UMons), Belgium (Publicity co-chair) Anthony Cleve, University of Namur (UNamur), Belgium (Co-organizer) Program Committee members Alexandre Bergel, University of Chile, Chile Carolin Brandt, Delft University of Technology, Netherlands John Businge, University of Antwerp, Belgium Gemma Catolino, Jheronimus Academy of Data Science, Netherlands Anthony Cleve, University of Namur, Belgium Alexandre Decan, University of Mons, Belgium Xavier Devroey, University of Namur, Belgium Felipe Ebert, Jheronimus Academy of Data Science, Netherlands Maliheh Izadi, Delft University of Technology, Netherlands Julia Lawall, Inria-Whisper, France Ivano Malavolta, Vrije Universiteit Amsterdam, Netherlands Kim Mens, Ecole Polytechnique de Louvain, Belgium Alexander Serebrenik, Eindhoven University of Technology, Netherlands Damian Andrew Tamburri, Eindhoven University of Technology, Netherlands Andy Zaidman, Delft University of Technology, Netherlands Vadim Zaytsev, Universiteit Twente, Netherlands Ahmed Zerouali, Vrije Universiteit Brussel, Belgium