Explainable persuasion helps share information about the persuasive design techniques used in a system to change or shape attitudes and/or behaviours. This study examined how aware people who gamble online are of persuasive design techniques used by online gambling platforms, and how they felt about explainable persuasion. A total of 250 adults in the UK who gambled regularly completed a survey. Most people knew how online gambling platforms used different persuasive design techniques (e.g., in-game rewards, reminders, and praise). Most people were also aware of the intention of these techniques and the potential harm. Most people believed that explainable persuasion could help them stay in control of their gambling. Over half believed it would make them feel more positive towards gambling operators. Many thought explainable persuasion could also remind them of the possible side effects of persuasive techniques.