Summary COVID-19 misinformation has spread rapidly across social media. To counter misinformation, we designed a short, wordless and animated video (called the CoVideo) to deliver scientifically informed and emotionally compelling information about preventive COVID-19 behaviours. After 15 163 online participants were recruited from Germany, Mexico, Spain, the UK and the USA, we offered participants in the attention placebo control (APC) and do-nothing arms the option to watch the CoVideo (without additional compensation) as post-trial access to treatment. The objective of our study was to evaluate participant engagement by quantifying (i) the proportion of participants opting to watch the CoVideo and (ii) the duration of time spent watching the CoVideo. We quantified the CoVideo opt-in and view time by experimental arm, age, gender, educational status, country of residence and COVID-19 prevention knowledge. Overall engagement with the CoVideo was high: 72% of the participants [CI: 71.1%; 73.0%] opted to watch the CoVideo with an average view time of 138.9 out of 144.0 s [CI: 138.4; 139.4], with no statistically significant differences by arm. Older participants (35–59 years) and participants with higher COVID-19 prevention knowledge had higher view times than their counterparts. Spanish participants had the highest opt-in percentage whereas Germans exhibited the shortest view times of the five countries. Short, wordless and animated storytelling videos, optimized for ‘viral spread’ on social media, can enhance global engagement with COVID-19 prevention messages by transcending cultural, language and literary barriers.