Flow chart: schematic overview of the selection process for apps eligible for full review. This flow chart provides a schematic overview of the selection process of eligible apps available in iTunes and Google Play (GP). The initials of the main reviewers are reported as JM and AM. aApps on the list of one researcher were untraceable for the other researcher. bApps to which the adjusted screening method had been applied and only the titles were screened. cApps that were not available in English or Dutch. dThe main focus of the apps was not physical activity (PA) promotion. eApps that focused on diet and weight loss. fThe main focus of the apps was not physical activity (PA) promotion or weight loss. gApps that targeted people with injuries or disabilities. hApps that targeted children or older adults. iApps did not follow the guidelines for physical activity. jApps that did not provide tailored feedback. kApps that were detected in the first screening step and were not available for download. lAfter downloading the app, it did not work. mAn extra monitor or device was needed to receive tailored feedback. nBefore using the app, a credit card was needed to deduct money as a penalty if the user did not achieve self-defined goals. oThe same app was available under a different name but with the same features. pThe app had a free and a paid version, but the paid version did not have additional features.