Predicting the sealing capacity of faults and caprocks has been a long-standing uncertainty for those involved in the exploration, appraisal and development of petroleum reservoirs. In more recent years, interest in the topic has increased in a wide range of other applications, particularly those related to the decarbonization of our energy supply such as carbon capture and storage (CCS), radioactive waste disposal, geothermal energy production and underground energy storage (e.g. compressed air, hydrogen). Knowledge of how faults impact fluid flow is also important for management of drinking water supplies. To communicate new advances in research in these areas, the EAGE organized the first international conference on Fault and Top Seals in 2003. These conferences have continued to be held at roughly 4 yearly intervals and have brought together scientists from a wide range of disciplines to discuss new research findings and workflows relevant to predicting fault and top seal behaviour, as well as presenting case studies covering both successful and unsuccessful attempts to predict sealing capacity.Thematic collection: This article is part of the Fault and top seals collection available at: https://www.lyellcollection.org/cc/fault-and-top-seals-2019