Around 300,000 people from around the world have expressed an interest in the University of Edinburgh's free taster sessions.
The figure emerged seven weeks after the university hit the 200,000 milestone.
The institution is part of the wider Coursera consortium, set up by US academics to provide web-based undergraduate-level courses to anyone who wants to do them.
Edinburgh, which joined the consortium last summer, is offering six courses across the humanities, engineering and science.
Known as massive open online courses (Moocs), the subjects covered include astrobiology and the search for extra-terrestrial life, artificial intelligence, philosophy and equine nutrition.
The courses are described as tasters for people interested in higher education but who are not in a position to enter it full-time. They have no entry requirements, run for five weeks (seven for philosophy) and are still open for enrolment.