Findings and lessons learned from the piloting of an on-device app to prevent the viewing of child sexual abuse material

Online child sexual abuse material (CSAM) offending has reached unprecedented levels to which traditional law enforcement cannot adequately respond. In reaction to calls for preventative efforts, the Protech project developed an app (“Salus”) to support individuals at risk of CSAM offending. Salus is voluntarily downloaded to personal devices and can block CSAM and (optionally) adult sexual content, in real time. We conducted an evaluation of the intervention, which was delivered alongside existing therapeutic support, in Belgium/Flanders, Germany, and the United Kingdom (UK) in 2024–2025 adopting the RE-AIM framework (Reach, Effectiveness, Adoption, Implementation, Maintenance). Participants reported positive experiences when engaging with some aspects of the app (such as privacy and security features, and block notifications) and some reported benefits; however, some participants reported experiencing technological challenges associated with the app, which reduced its usefulness. Our study highlights the importance of thorough real-world testing of CSAM blocking apps to ensure app effectiveness.PRACTICE IMPACT STATEMENT Our study highlights that on-device apps to reduce CSAM viewing are feasible and can reduce individuals’ desire to view CSAM. However, on-device technology requires extensive real-world testing and refinement before it is further rolled out to at-risk individuals for the purpose of CSAM prevention. In addition, on-device technology also requires extensive monitoring and evaluation of its benefits, both as a stand-alone tool, and as one tool in a wider prevention toolbox.