Purpose
Mass media HIV testing interventions are effective in increasing testing, but there has been no examination of their theory or behaviour change technique (BCT) content. Within a heterogeneous body of studies with weak evaluative designs and differing outcomes, we attempted to gain useful knowledge to shape future interventions.

Methods
Within a systematic review, following repeated requests to the authors of included studies for intervention materials, the Theory Coding Scheme, the Theoretical Domains Framework (TDF), and Behaviour Change Technique Taxonomy (BCTT) were used to extract data relating to active intervention content.

Results
Of 19 studies, five reported an explicit theoretical basis to their intervention. TDF analysis highlighted the key domains employed within the majority of interventions: ‘knowledge’, ‘social roles and identities’, and ‘beliefs about consequences’. BCT analysis showed three BCT groupings commonly reported within interventions: ‘Comparison of outcomes’, ‘Natural consequences’, and ‘Shaping knowledge’. Three individual BCTs formed the backbone of most interventions and can be considered ‘standard’ content: ‘Instructions on how to perform behaviour’; ‘Credible source’; and ‘Information about health consequences’.

Conclusions
This is the first study to examine and detail active intervention content in this field. It suggests future interventions should improve knowledge about testing, and use well‐branded and trusted sources that endorse testing. Future interventions should also provide clear information about the health benefits of testing. Our analysis also suggests that to improve levels of effectiveness characterizing the current field, it may be useful to elicit commitment, and action plans, relating to how to implement testing intentions.