eBook Readers and Digital File Formats

eBook files come in a variety of formats for use on various tablets and ereader devices and software. The information below is provided as guidance only., so be sure to choose the correct format for your device and eBook reading software program and follow the instructions for your specific device or software.

SIDE-LOADING: To read an eBook file from the U.S. Government Bookstore website on a dedicated eReader like a Kindle, Nook or Sony eReader, or on a tablet such as an Apple iPad, Kindle Fire, or Samsung Galaxy, users will need to manually "sideload" or copy the downloaded file to their eReader or mobile device.

Table of Contents:


What is the EPUB Format?

EPUB (short for electronic publication) is a free and open eBook standard by the International Digital Publishing Forum (IDPF) that is based on XHTML, XML and CSS.  EPUB eBook files have the extension .EPUB.

EPUB is designed for reflowable content, meaning that an EPUB reader can optimize text for a particular display device. EPUB also supports fixed-layout content. The format is intended as a single format that publishers and conversion houses can use in-house, as well as for distribution and sale. It is the most popular eBook format as it can be used on multiple devices.

What is the MOBI Format?

MOBI format was invented by French company MobiPocket as an ebook format for their MobiPocket Reader application. The company was bought by Amazon and used in Amazon's Kindle eBook reader devices.  MOBI files usually have .mobi extension. Because the format was originally designed for Palm Pilot PDAs, they can also have .prc or .pdb extension.

Amazon's eBooks sometimes have an .AZW extension which is an earlier version of the MOBI file format. But Amazon added DRM (Digital Rights Management) to their version of the MOBI format, which means that AZW eBooks purchased directly from Amazon can ONLY be read by Amazon's Kindle software or devices.

However, MOBI format files can be read on Kindles and any other MOBI-capable devices and software.

What is PDF format?

Invented by Adobe Systems in 1993, Portable Document Format (PDF) is now an open standard for electronic document exchange maintained by the International Organization for Standardization (ISO).

When you convert documents, forms, graphics, and web pages to PDF, they look just like they would if printed. But unlike plain printed documents, enhanced PDF files can contain clickable links and buttons, form fields, video, and audio — as well as logic to help automate routine business processes.

When you share a PDF file, virtually anyone can read it using the free Adobe Reader® computer software or the free Adobe Reader® mobile app.


Below are some FREE eBook reader software programs that can be used to read eBooks downloaded from this site, on either desktop/ laptop computers or mobile devices. 

Desktop-Only eBook Reader Software

Download and install these free software programs in order to read eBook files on your desktop or laptop computer. 

  • Calibre is a free and open source desktop eBook library management application developed by users of eBooks for users of eBooks. It can manage your eBook library, sync files to a number of different devices and even convert between eBook formats.
    • Supported Output Formats: AZW3, EPUB, FB2, OEB, LIT, LRF, MOBI, HTMLZ, PDB, PML, RB, PDF, RTF, SNB, TCR, TXT, TXTZ
    • Supported Platforms:  Windows, Mac OS X, Linux

Click here for more information and to download Calibre.

  • Adobe Digital Editions is a free desktop eBook reader software program from Adobe Systems for reading EPUB and PDF documents. It is used for acquiring, managing and reading eBooks, digital newspapers, and other digital publications. It can render and format the text correctly and clearly, support multiple bookmarks, create a local library, sort books, customize the size of text to the way you like. Once installed on your computer, this free EPUB viewer will open EPUB files for you automatically. Note: Books can be copied from one device to another device only if the same Adobe Digital Editions ID is used.
    • Supported Formats: PDF, EPUB (XHTML)
    • Supported Platforms:  Windows, Mac OS X

Click here for more information and to download Adobe Digital Editions.

  • Sumatra PDF is a small reader for Windows computers that can view PDF, eBook (EPUB, Mobi), XPS, DjVu, CHM, and Comic Book (CBZ and CBR) files.
    • Supported Formats: PDF, EPUB, MOBI, XPS, DjVu, CHM, and Comic Book (CBZ and CBR)
    • Supported Platforms:  Windows 

Click here for more information and to download Sumatra PDF.

Web Browser Extensions

Add these extensions to your Internet web browser in order to be able to read these files from your browser.

  • EPUBReader Add-On for Firefox: EPUBReader is a free add-on for the Firefox Web browser and Firefox Mobile browser that can directly open any EPUB format.
    • Supported Formats: EPUB
    • Supported Platforms:  Windows, Mac OS X, Linux.

HOW TO INSTALL: Open Firefox. Click on the EPUBReader Add-ons extension page and click the green button ‘Add to Firefox’ to install. When installation is complete, you will see an additional button appear at the top right corner of your Firefox browser (will say ‘EPUB –Catalog’ on mouseover), click the button to launch EPUBReader.

HOW TO INSTALL: Open Google Chrome browser. To start reading ebook from your Chrome browser, click on the MagicScroll extension page link on the Chrome Web Store, then click on the ‘Add to Chrome’ button to install. Once installed, you can open a new tab in your Chrome browser and go to this web address: MagicScroll.net

Mobile Device eBook Readers

Download and install these apps in order to be able to read eBooks on your mobile device.

  • Bluefire Reader allows users to read Adobe eBooks from retailers, publishers and libraries around the world. Adobe eBooks are PDF and ePUB files that have been copy-protected with Adobe Digital Rights Management (DRM) software. These files are also referred to as Adobe Content Server 4 (ACS4) documents.
    • Supported Formats:  EPUB and PDF.
    • Supported Platforms:
    • Transferability: Adobe eBooks that have been downloaded to other computers or devices can often be transferred to Bluefire Reader if the same Adobe ID was used to authorize each device.  Note: an exception to this may occur if the book publisher has elected to limit the reading rights of a book to a single device, making them non-transferrable. 
    • To get an Adobe ID, either go to the Adobe site and register or use the the Authorization Dialog in Bluefire Reader once you install it.
    • For more information, read the Bluefire Reader User Guide.
  • FBReader is a multi-platform eBook reader that supports several free eBook formats.
    • Supported Formats: EPUB and EPUB 3, MOBI (non-DRM), fb2 (.zip), plain text, HTML, most RTF and MS-Word DOC, and PDF (coming soon).
    • Supported Platforms:  Windows, Mac OS X, Linux, Android, Blackberry 10.
  • Cool Reader is a cross-platform XML/CSS based eBook reader for desktops and handheld devices.
    • Supported Formats: EPUB (non-DRM), MOBI (non-DRM), TXT, RTF, DOC, TCR, HTML, PML, CHM, PDB, PRC, FB2.
    • Supported Platforms: Win32, Linux, Android.
  • NeoSoar eBooks, PDF & ePub Reader is an Apple iOS PDF & ePub reader, support PDF, ePub, Adobe DRM eBooks open in, no need to sign in to use, it can import your favorite or any Internet download PDF and ePub,
    • Supported Formats: EPUB (non-DRM), PDF, Adobe DRM.
    • Supported Platforms: Compatible with iPhone, iPod touch, and iPad. Requires iOS 5.0 or later.

Disclaimer: The hypertext links on this page will allow you to leave this Federal Government web site. The links are provided as a service to users and are not sponsored by or affiliated with this web site or under the control of the GPO. The links are to be accessed at the user’s own risk, and GPO makes no representation or warranties about the content of these links. GPO is not responsible for the content of any linked site, including any software contained therein, or any link contained in a linked site. GPO is providing these links to you only as a convenience, and the inclusion of any link does not imply endorsement by GPO of the site.

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