This book constitutes the proceedings of the 25th International Conference on Descriptional Complexity of Format Systems, DCFS 2023, which took place in Potsdam, Germany, in July 2023.The 14 full papers, including one invited presentation as a full paper, presented in this volume were carefully reviewed and selected from 16 submissions.

Operational State Complexity Revisited: the Contribution of Monsters and Modifiers.- Hypercubes and Isometric Words based on Swap and Mismatch Distance.- Defying Gravity and Gadget Numerosity: The Complexity of the Hanano Puzzle.- Existential and Universal Width of Alternating Finite Automata.- On Jaffe’s Pumping Lemma, Revisited     .- Operational Complexity: NFA-to-DFA Trade-Off.- The Word Problem for Finitary Automaton Groups.- Separating Words Problem over Groups.- Complexity of Exclusive Nondeterministic Finite Automata.- Shortest Accepted Strings for Two-Way Finite Automata: Approaching the  Lower Bound.- Pushdown and One-Counter Automata: Constant and Non-Constant Memory Usage.- Construction of a Bi-Infinite Power Free Word with a Given Factor and a Non-Recurrent Letter.- Merging two Hierarchies of External Contextual Grammars with Subregular Selection.- A Tight Upper Bound on the Length of Maximal Bordered Box Repetition-Free Words.