Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: “Youth were then randomly selected by the research team using randomizer.org.” Comment: random sequence generation was adequately done
Allocation concealment (selection bias)	Low risk	Quote: “Participants were randomised at the end of the baseline survey. As such, all participants were blind to their arm assignment at enrolment.” Comment: allocation concealment was adequate
Similar baseline characteristics	Unclear risk
Similar baseline outcome measurement	Unclear risk
Blinding of participants and personnel (performance bias)	Low risk	Comment: blinding was not possible due to the nature of the intervention
Blinding of outcome assessment (detection bias)	Unclear risk	Comment: insufficient information to permit judgement
Incomplete outcome data (attrition bias)	Low risk	Quote: “Ninety‐two percent of intervention and 93% of control participants provided six‐month follow‐up data” Comment: missing outcome data is balance across the groups
Prevention of knowledge of allocated intervention	Unclear risk
Protection against contamination	Unclear risk
Selective reporting (reporting bias)	Low risk	Quote: “The study design initially proposed to examine the effects of exposure to CyberSenga on unprotected sex over the six‐month follow‐up period. Based upon the decision to deliver the final module as a booster, the main outcome measure was modified, prior to study implementation, to be unprotected sex in the past three months at six‐months' post‐intervention.” Comment: outcome was modified but was adjusted appropriately with the changes to the methods.
Other bias	Low risk	Comment: insufficient information to permit judgement