This two-volume set LNCS 12789 and 12790 constitutes the refereed proceedings of the Third International Conference on HCI in Games, HCI-Games 2021, held as part of the 23rd International Conference, HCI International 2021, which took place in July 2021. Due to COVID-19 pandemic the conference was held virtually. The total of 1276 papers and 241 posters included in the 39 HCII 2021 proceedings volumes was carefully reviewed and selected from 5222 submissions. The papers of HCI-Games 2021, Part I, are organized in topical sections named: Experience Design in Games; User Engagement and Game Impact; Game Mechanics.

This book constitutes the refereed proceedings of the Third International Conference on HCI in Mobility, Transport, and Automotive Systems, MobiTAS 2021, held as part of the 23rd International Conference, HCI International 2021, held as a virtual event, in July 2021. The total of 1276 papers and 241 posters included in the 39 HCII 2021 proceedings volumes was carefully reviewed and selected from 5222 submissions. MobiTAS 2021 includes a total of 39 papers which focus on topics related to urban mobility, cooperative and automated mobility, UX in intelligent transportation systems, and mobility for diverse target user groups.

This book constitutes late breaking papers from the 23rd International Conference on Human-Computer Interaction, HCII 2021, which was held in July 2021. The conference was planned to take place in Washington DC, USA but had to change to a virtual conference mode due to the COVID-19 pandemic. A total of 5222 individuals from academia, research institutes, industry, and governmental agencies from 81 countries submitted contributions, and 1276 papers and 241 posters were included in the volumes of the proceedings that were published before the start of the conference. Additionally, 174 papers and 146 posters are included in the volumes of the proceedings published after the conference, as “Late Breaking Work” (papers and posters). The contributions thoroughly cover the entire field of HCI, addressing major advances in knowledge and effective use of computers in a variety of application areas.

This book constitutes late breaking papers from the 23rd International Conference on Human-Computer Interaction, HCII 2021, which was held in July 2021. The conference was planned to take place in Washington DC, USA but had to change to a virtual conference mode due to the COVID-19 pandemic. A total of 5222 individuals from academia, research institutes, industry, and governmental agencies from 81 countries submitted contributions, and 1276 papers and 241 posters were included in the volumes of the proceedings that were published before the start of the conference. Additionally, 174 papers and 146 posters are included in the volumes of the proceedings published after the conference, as “Late Breaking Work” (papers and posters). The contributions thoroughly cover the entire field of HCI, addressing major advances in knowledge and effective use of computers in a variety of application areas.

The two-volume set LNCS 12765-12766 constitutes the refereed proceedings of the thematic area Human Interface and the Management of Information, HIMI 2021, which was held as part of HCI International 2021 and took place virtually during July 24-29, 2021. The total of 1276 papers and 241 posters included in the 39 HCII 2021 proceedings volumes was carefully reviewed and selected from 5222 submissions. The papers included in the HCII-HIMI volume set were organized in topical sections as follows: Part I: Information presentation; visualization and decision making support; information in VR and multimodal user interfaces; Part II: Learning in information-rich environments; supporting work, collaboration and design; intelligent information environments.

The two-volume set LNCS 12765-12766 constitutes the refereed proceedings of the thematic area Human Interface and the Management of Information, HIMI 2021, which was held as part of HCI International 2021 and took place virtually during July 24-29, 2021. The total of 1276 papers and 241 posters included in the 39 HCII 2021 proceedings volumes was carefully reviewed and selected from 5222 submissions. The papers included in the HCII-HIMI volume set were organized in topical sections as follows: Part I: Information presentation; visualization and decision making support; information in VR and multimodal user interfaces; Part II: Learning in information-rich environments; supporting work, collaboration and design; intelligent information environments.

This two-volume set constitutes the refereed proceedings of the 7th International Conference on Human Aspects of IT for the Aged Population, ITAP 2021, held as part of the 23rd International Conference, HCI International 2021, held as a virtual event, in July 2021. The total of 1276 papers and 241 posters included in the 39 HCII 2021 proceedings volumes was carefully reviewed and selected from 5222 submissions. ITAP 2021 includes a total of 67 papers; they focus on topics related to designing for and with older users, technology acceptance and user experience of older users, use of social media and games by the aging population, as well as applications supporting health, wellbeing, communication, social participation and everyday activities.

This two-volume set LNCS 12774 and 12775 constitutes the refereed proceedings of the 13th International Conference on Social Computing and Social Media, SCSM 2021, held as part of the 23rd International Conference, HCI International 2021, which took place in July 2021. Due to COVID-19 pandemic the conference was held virtually. The total of 1276 papers and 241 posters included in the 39 HCII 2021 proceedings volumes was carefully reviewed and selected from 5222 submissions. The papers of SCSM 2021, Part I, are organized in topical sections named: Computer Mediated Communication; Social Network Analysis; Experience Design in Social Computing.

This book constitutes the refereed proceedings of the 18th International Conference on Engineering Psychology and Cognitive Ergonomics, EPCE 2021, held as part of the 23rd International Conference, HCI International 2021, held as a virtual event, in July 2021. The total of 1276 papers and 241 posters included in the 39 HCII 2021 proceedings volumes was carefully reviewed and selected from 5222 submissions. EPCE 2021 includes a total of 34 papers; they were organized in topical sections named: cognitive psychology in aviation; cognitive psychology in air traffic control; studies on cognitive processes; human error and human performance; and cognition and design.

This book constitutes the refereed proceedings of the 13th International Conference on Virtual, Augmented and Mixed Reality, VAMR 2021, held virtually as part of the 23rd HCI International Conference, HCII 2021, in July 2021. The total of 1276 papers and 241 posters included in the 39 HCII 2021 proceedings volumes was carefully reviewed and selected from 5222 submissions. The 47 papers included in this volume were organized in topical sections as follows: designing and evaluating VAMR environments; multimodal and natural interaction in VAMR; head-mounted displays and VR glasses; VAMR applications in design, the industry and the military; and VAMR in learning and culture.