(Left) Total number of attendees, and (right) total number of countries the attendees participated from. Shown are the typical in-person (year 2019) and 2020 virtual attendee counts for annual meetings of American Association for Cancer Research (AACR), American Society of Clinical Oncology (ASCO), European Geosciences Union (EGU), AIDS biennial conference, The Endocrine Society (ENDO), American Society for Nutrition (ASN), American Diabetes Association (ADA), Alzheimer's Association International Conference (AAIC), American Society for Human Genetics (ASHG), American Society for Mass Spectrometry (ASMS), American Society for Plant Biology (ASPB), International Conference for Learning Representation (ICLR), International Conference for Machine Learning (ICML), Research in Computational Molecular Biology (RECOMB), Society for Developmental Biology (SDB), the quadrennial meeting of the Genetics Society of America (TAGC), Joint Statistical Meetings (JSM) of the American Statistical Association, Society for Imaging Informatics in Medicine (SIIM), American Physical Society (APS) April meeting, the Ecological Society of America (ESA), the American Botanical Society meeting (Botany), American Society for Gene and Cell Therapy (ASGCT), American Psychological Association (APA). The American Association for Cancer Research (AACR) annual conference is attended by less than 24,000 scientists and clinicians in all subdisciplines of cancer research in-person every year. The AACR 2020 meeting took place in two parts virtually with over 100,000 attendees (Virtual Meeting I (April 27–28)) and (Virtual Annual Meeting II (June 22–24)) combined from 140 countries. At peak sessions, 24,000 attendees viewed the talks at the same time. Attendance at AACR 2020 was free for all (no registration fee for researchers or non-researchers). Available data on attendees and representing countries for in-person conferences held in years prior to 2019 are shown in Figure 3—figure supplement 2.