Although it supports unprotected Mobipocket books (.MOBI, .PRC), plain text files, and HTML and Word documents, Kindle also uses its own proprietary, DRM-restricted format (AZW). It does not fully support Portable Document Format (PDF), but Amazon provides "experimental" conversion to the native AZW format. Users may also convert PDF files to supported formats using third-party software.
Using the experimental web browser, it is possible to download books directly on the Kindle (.mobi, .prc and .txt). Hyperlinks in a Mobipocket file can be used to download e-books but cannot be used to reference books stored in the Kindle's memory.
The Kindle charges monthly for RSS subscription to select blogs, even though users may use the experimental web browser to navigate to and read blogs or any other web pages free of charge.Stanza is a Windows and Mac compatible application that is used for both portable e-book file format reading and conversion. It includes conversion into the Kindle AZW format. Stanza is currently in beta, it is expected to cost $15 per license once it reaches release status.