OER Knowledge CloudConference PaperCheung, Simon K. S.Evolved as open courseware, open online courses and tutorials, open access e-books and open source learning tools, open educational resources or OER are generally perceived as useful resources by university students. Over the last year, many higher education institutions have rapidly switched their usual classroom-based learning to online learning in order to accommodate the social distancing requirements arising from the outbreak of COVID-19. This paper investigates the implication on the students’ perceived usefulness of OER after the switch to online learning. Based on two identical surveys conducted in a university in Hong Kong before and after the change, it is revealed that the students’ perceived usefulness was generally increased, where the increase in perceived usefulness was more significant on open online complete courses, online tutorials, and open access e-books than other types of OER. It is also revealed that the students have become more aware of the shortcomings of OER, especially on accuracy and comprehensiveness. OER, especially open online courses, tutorials, and open access textbooks, are perceived to be useful for students to accommodate a rapid shift to online learning mode.20212021/08/03EnglishSpringer, Cham298-308Hong Kong10.1007/978-3-030-80504-3_25978-3-030-80504-3yesopen educational resourcesopen coursewareonline coursesopen access e-bookslearning toolsonline learninglearning effectivenessHong Kong, Asia