Non-formal, yet educative, activities such as science festivals can positively influence the public regarding their attitude towards Science, Technology, Engineering and Math (STEM) subjects and students' willingness to pursue STEM-related careers. We evaluate the changes made to adapt the Oxford Brookes Science Bazaar, a science festival that has been delivered face-to-face since 2008, to a virtual format in 2021 due to the COVID-19 pandemic. The online festival included 28 pre-recorded and 12 live activities of different types (hands-on, demonstration, games, lectures, podcasts, virtual tours). Hands-on activities and virtual tours had the highest number of unique viewers, while lectures and podcasts were the least watched. The videos were watched also after the advertised date of the festival and reached a broader audience than the physical events. The number of participants, the holding time, and the proportion of people who filled the feedback forms, however, were lower in the online than the physical events. STEM organisations should consider hybrid events, with both virtual and in-person contents, to reach a broader audience and to create more inclusive events. We provide recommendations on how to maximise the benefit of virtual formats, including expanding blended virtual activities to reach a wider variety of age groups.