The collaborative outcomes study on health and functioning during infection times in adults (COH-FIT-Adults): Design and methods of an international online survey targeting physical and mental health effects of the COVID-19 pandemic

•The Collaborative Outcome study on Health and Functioning during Infection Times (COH-FIT) is the broadest survey on COVID-19 impact to date, involving over 230 researchers and 120 institutions across the six continents.•COH-FIT is an online anonymous survey, cross-sectional at the individiual level, but longitudinal at the population level, and has a multi-wave structure.•COH-FIT is available in 30 languages, being inclusive towards linguistic and ethnic minorities.•COH-FIT collects responses from adults, adolescents, and children starting from 6 years old.•COH-FIT collects both representative sample via polling agencies, and non-representative samples via snowball/non-probability recruiting approach.•COH-FIT has been collecting over 150,000 responses from over 150 countries, from the six continents from April 26th, 2020 to July 23rd, 2021.•Take the survey at www.coh-fit.com.