The most popular ebook formatting is the EPUB (Electronic Publication) format. EPUB is widely used and supported by major ebook retailers and reading devices, including Amazon Kindle, Apple Books, Kobo, and Barnes & Noble Nook. EPUB offers flexible layout options, supports reflowable text, and allows readers to customize their reading experience. It also supports interactive features like bookmarks, annotations, and hyperlinks. EPUB files can be easily created and converted using various ebook creation tools and software. While other formats like MOBI and PDF also have their uses, EPUB remains the go-to format for most ebooks due to its versatility and broad compatibility.