This is the first release of PeakSwift. The Swift library is designed for accurate and computationally efficient detection of R-peaks in single-lead electrocardiogram signals and was developed primarily for the iOS platform. In addition to 9 common algorithms for detecting R-peaks, there are two methods for estimating signal quality and an extensible skeleton for context-dependent selection of algorithms, e.g., the most powerful algorithm for atrial fibrillation.