ReadLingo is a free Chrome add-on designed to assist users in managing and learning new vocabulary efficiently. It features local-first management of vocabulary words, allowing for unlimited storage without data collection concerns. Users can highlight unfamiliar words on web pages using customizable styles and seamlessly sync their vocabulary with the Youdao Dictionary through an API for a more integrated learning experience.

The application offers a range of tools to enhance vocabulary acquisition, including word grouping with distinct highlight styles for each category. It also incorporates a large language model to provide contextual understanding of new words. Additional features include word translation, quick lookup options, and a spelling check to reinforce learning, with celebratory UI elements to acknowledge each mastered word.