AbstractObjectiveFraudulent participation is an escalating concern for online clinical trials and research studies and can have a significant negative impact on findings. We aim to shed light on the risk and to provide practical recommendations for detecting and managing such instances.MethodsThe FREED‐Mobile (FREED‐M) study is an online, randomized controlled feasibility trial to assess a digital early intervention for young people (aged 16–25) in England or Wales with eating problems. The trial involved baseline (week 0), post‐intervention (week 4), and follow‐up (week 12) surveys, alongside weekly modules provided over 4 weeks on the study website. Study completers were compensated with £20 shopping vouchers. Despite the complexity of the trial design, two instances of fraudulent sign‐ups occurred in January and March 2023. To counter this, we developed a “fraudulent participants protocol” following internal investigations and discussions with collaborators.ResultsThe implementation of prevention measures such as reCAPTCHA updates, IP address review, and changes in reimbursement effectively halted further fraudulent sign‐ups. Our protocol facilitated the systematic identification and withdrawal of suspected or clear fraudsters and was demonstrably robust at distinguishing between fraudsters and genuine responders.DiscussionAll remote, online trials or studies are at risk of fraudulent participation. Drawing from our experience and existing literature, we offer practical recommendations for researchers considering online recruitment and data collection. Vigilance and the integration of deterrents, and data quality checks into the study design from the outset are advised to safeguard research integrity.Public SignificanceFraudulent participation in digital research can have asignificant impact on research findings, potentially leading to biased resultsand misinformed decisions. We developed an effective protocol for theprevention, identification, and management of fraudulent participants. Bysharing our insights and recommendations, we hope to raise awareness of thisissue and provide other researchers with the knowledge and strategies necessaryto safeguard research integrity moving forward.