MOBI and EPUB are file formats designed specifically for eBooks, enabling features like adjustable text size and layout reflow to fit different screen sizes. MOBI, developed by Mobipocket and later acquired by Amazon, was historically the primary format for Kindle devices. EPUB (Electronic Publication) is an open standard managed by the International Digital Publishing Forum (IDPF), built using web technologies like HTML and CSS, allowing broad compatibility beyond a single vendor.

Specialized e-reader hardware, like Amazon Kindles (opening MOBI) or devices from Kobo, Barnes & Noble Nook, and PocketBook (opening EPUB), are common tools. Software solutions include desktop applications (Adobe Digital Editions, Calibre), mobile apps (Apple Books on iOS, Google Play Books on Android), and web browsers using EPUB readers. Library platforms like OverDrive/Libby primarily distribute EPUB eBooks for lending.

EPUB is now the dominant open standard, offering extensive features and interoperability, while MOBI support is declining (Amazon now favors sending EPUB files or their newer KF8/AZW3 formats to Kindle, automatically converting any MOBI uploaded). Limitations involve potential DRM restrictions preventing copying or sharing. The widespread adoption of EPUB fosters accessible digital reading across numerous devices and services.