Objective: The inclusion and design of age restriction warnings, harm reduction messages, and terms and conditions (T&Cs) in gambling advertising is self-regulated in the United Kingdom. Our study examines the visibility and nature of this information in a sample of paid-for gambling adverts. Study design: Content analysis of a stratified random sample of gambling adverts (n=300) in the United Kingdom from eight paid-for advertising channels (March 2018). Methods: For each advert, we assessed whether any age restriction warnings, harm reduction messages, and T&Cs were present. If so, visibility was scored on a five-point scale ranging from Very poor (<10% of advert space) to Very good (>25% of advert), which had high inter-rater reliability. Descriptive information on position, design, and tone of language was recorded. Results: One-in-seven adverts (14%) did not feature an age restriction warning or harm reduction message. In adverts that did, 84% of age restriction warnings and 54% of harm reduction messages had very poor visibility. At least one-in-ten adverts did not contain T&Cs. In adverts that did, 73% had very poor visibility. For age restriction warnings, harm reduction messages, and T&Cs, most appeared in small fonts and outside the main advert frame. Most harm reduction messages did not actually reference gambling-related harms. Conclusion: Age restriction warnings, harm reduction messages, and T&Cs do not always appear in paid-for gambling advertising. When they do, visibility is often very poor and the messaging not clear. The findings do not support a self-regulatory approach to managing this information in gambling adverts.