CastReader is a browser extension and mobile app that reads webpages, PDFs, Kindle books, and AI chatbot responses aloud using natural AI voices with word-by-word highlighting in 9 languages. It includes a Read and Explain feature that summarizes difficult or foreign-language passages while a visual pen marks key points on the original text. CastReader supports Google Docs, Gmail, Notion, and major AI platforms like ChatGPT, Claude, and Gemini, adding per-response listen buttons to each. A free tier allows 20 minutes of daily listening, while a Pro plan removes caps and unlocks premium voices and full ebook support.