This book constitutes the refereed proceedings of the 30th International Conference on Developments in Language Theory, DLT 2026, held in Rouen, France, during June 30 – July 3, 2026.The 22 full papers and 3 invited papers included in this book were carefully reviewed and selected from 49 submissions. They present current developments in the field of formal language theory and its applications.

This book constitutes the refereed proceedings of the 30th International Conference on Developments in Language Theory, DLT 2026, held in Rouen, France, during June 30 – July 3, 2026.The 22 full papers and 3 invited papers included in this book were carefully reviewed and selected from 49 submissions. They present current developments in the field of formal language theory and its applications.

This book constitutes the refereed proceedings of the 30th International Conference on Developments in Language Theory, DLT 2026, held in Rouen, France, during June 30 – July 3, 2026.The 22 full papers and 3 invited papers included in this book were carefully reviewed and selected from 49 submissions. They present current developments in the field of formal language theory and its applications.