This study aimed to compare and contrast Taiwanese EFL (English as a foreign language) college freshmen’s perceptions of and attitudes toward three online vocabulary flashcard websites. Nakata’s (2011) “Criteria for Evaluating Flashcard Software” and Nation’s (1994) “Activities for Vocabulary Learning” were used to compare and contrast three online vocabulary flashcards and exercises in terms of the word knowledge acquired. The main results were the following two findings. First, these three online vocabulary flashcards mainly focused on Nation’s (1994) form and words’ meaning. These online exercises and flashcards met eight of Nakata’s (2011) 17 criteria. Second, participants held positive attitudes toward learning and improving their vocabulary abilities via online flashcards and their related activities. Speller in Quizlet was the most popular activity chosen by participants, followed by Test, Scatter, and Space Race in Quizlet. Four suggestions are provided to make online flashcards more effective vocabulary-learning tools: provision of user-friendly guidelines on using online flashcards, provision of flashcards with word meanings and related information, multiple modalities of presentation on vocabulary flashcards, and a variety of activity designs in interactive vocabulary exercises.