Problem. The experience of using online applications for mastering vocabulary in foreign language classes at universities is studied. The main components of Quizlet innovative technology and examples of its use are presented in the article. The advantages and disadvantages of using the Quizlet mobile application in teaching a foreign language are analysed. Efficiency of implementing this application in educational process and in extracurricular use in the conditions of modern education is discussed. Goal. The purpose of the work is to study and analyse all the possibilities of implementing the Quizlet mobile application in the process of teaching a foreign language, including vocabulary enlargement. The advantages and disadvantages of this application are selected. Methodology. The tasks and specifics of the object under study led to the use of synchronous-descriptive method with elements of comparative analysis, simulation method, which contributed to the comprehensive study of the problem. Results. Having analysed all the advantages and disadvantages of using the Quizlet mobile application, we came to the conclusion that the mobile application actually brings more benefits to the classroom and promotes students’ interest and involvement in the learning process. Thanks to the phone, which is familiar to young people, the use of the mobile application in learning vocabulary offers a flexible timetable for fulfilling the task, the availability of study at any time, since the phone is always with the student, access to a set of necessary educational materials in a modern electronic form. The use of the mobile application in both the classroom and extracurricular activities increases the student’s self-organization, which is extremely relevant today, because in higher education there is a reduction in the number of classroom hours and an increase in hours given to students’ independent extracurricular work. Originality . For the first time possibilities of implementing the Quizlet mobile application in the process of teaching a foreign language, including vocabulary enlargement has been structured and comprehensively investigated, as well as the increase of students’ motivation to learn foreign languages by using mobile app in the educational process. Practical value. Implementing the Quizlet mobile application in the process of teaching a foreign language is a productive and effective innovation, because it makes the use of lexical material more efficient, allows to expand the opportunities for acquiring knowledge, promotes learning motivation, stimulates self-education, improves learning and information. Information resources of this type are inexhaustible and require further development by both teachers and students.