This paper addresses learning and development processes in online platform work. Specifically, it proposes a new instrument to survey and analyze self-regulated workplace learning in crowdwork, a type of online platform labor in which a global pool of workers are matched with clients through digital platforms to carry out remunerated tasks. Although workplace learning practices of workers in traditional, organisationally embedded jobs have been studied extensively, the findings cannot be transferred to describe and explain learning behaviors within crowdwork, which is fundamentally different from traditional work in that it is autonomous, radically distributed, and no organisationally provided training opportunities exist in crowdwork. To advance the understanding of workplace learning in crowdwork we reviewed the literature on workplace learning, platform work, and self-regulated learning to develop the Workplace Learning in Crowdwork Questionnaire, which we subsequently validated with 992 crowdworkers from six European countries on three crowdwork platforms. The instrument can be used by researchers to study the nature of (self-directed) workplace learning in online labor platforms. It can also be used by crowdworkers to self-reflect on their learning and development.