Illegal distribution of sexual images by adults and minors is an expanding problem. We examined whether messages would dissuade men (18-32 years) from visiting a fake website offering access to free pornography to users who uploaded a sexual image of a woman. Participants seeking to enter the site (n=528) were randomly assigned to one of three conditions. Group 1 went straight to the landing page. Group 2 encountered a text warning that sharing sexual images of people who appear under 18 years old is illegal; Group 3 received the same message with an accompanying animation. Sixty percent of Group 1 participants attempted to access the site, compared with 43 percent in Group 2 and 38 percent in Group 3. We argue that online messages offer a valuable strategy that can help reduce image-based abuse and the distribution of child sexual abuse material, including by minors.