Main outcome measures The primary outcome is whether the participant has taken up our HIVST-online service during a 6-month follow-up period. This behavioural outcome will recorded objectively by the HIVST administrators. Among those who had not taken up HIVST at Month 6, they will be contacted by social media to ask a few questions to assess secondary outcomes, which include: 1) whether having taken up any form of HIV testing other than HIVST-online and 2) intention to take up HIVST-online or other forms of HIV testing in the next six months. Process evaluation of the health promotion components (e.g., online video, MI, and project webpage) and the HIVST-online service (e.g., delivery of the HIVST kits, appointment making with HIVST administrators, pre- and post-test counseling) will also be conducted.