Caption literacy is the ability to use on-screen text for language learning purposes. The term captions refers to both same-language transcripts of audio and translations of audio into another language (often referred to as subtitles) added to a video consisting of sound and moving images. Captions appear across different digital platforms, including traditional media, streaming services, social media, and educational content. The availability of captions has opened up new opportunities for language learners to engage with authentic input. Research has shown the benefits of captions for language learning, such as improved comprehension, vocabulary acquisition, and listening skills. Artificial intelligence (AI) technology has enabled the automatic generation of captions, increasing access to authentic content but still requiring human oversight to review and correct any errors. Factors that influence caption literacy development include learner proficiency level, familiarity with captions, and awareness of learning needs when engaging with captions. Educators can foster caption literacy through learner training. Future research should investigate frameworks for developing caption literacy and explore the potential of personalised and adaptive learning strategies integrating AI-based technologies.