Indexes in ebooks can be ‘active’, with hyperlinks into the text. Should these links go to the page, paragraph, line or word level? This is a complex question, but the main concern may be the user interface in ebook reader applications. In this first article of a three-part series, Mary Coe and Jan Wright report on their investigation of how active ebook indexes are handled by ereader and Web browser software. They conclude that these applications are not yet offering a level of usability that takes full advantage of what active indexes can offer the reader.