Sideloading: What Is It?

Sideloading files between two devices

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Sideloading is one of those terms that's been around for a while and may have a slightly different meaning, depending on the context. Generally speaking, it dates back to the 1990s and belongs to a group of terms that developed with the Internet: upload, download and sideload. Sideload means transferring data directly between two devices, avoiding the process of downloading the data via the Internet. The most frequently used methods of sideloading are via a USB connection, through a Bluetooth connection or by copying data onto a memory card. 

Sideloading and E-Readers

E-Books are data files. In order to read an e-book, you must first transfer it onto a capable device such as an e-reader. While early generations of e-readers depended on sideloading to manage e-book collections, the current generation of devices is split into two camps. Sony continues to rely on sideloading for its most popular e-readers, the Reader Pocket Edition, and the Reader Touch. These devices lack Internet connectivity, so transferring e-books requires either a USB connection to a computer or copying e-books onto a memory card.

Other e-reader manufacturers have turned to downloading as the default method for loading e-books onto their devices. Amazon's Kindles, Barnes & Noble's Nook, and NOOK Color and Kobo's e-reader all offer Wi-Fi connectivity (and, in some cases 3G as well). Owners have accounts at the corresponding online e-book retailer and a record of their e-book purchases are maintained in the cloud. When they want to load a copy of an e-book onto their device, they log into their account through an Internet connection, buy the e-book (or select a title already in their collection) and it downloads onto their e-reader wirelessly. E-reader manufacturers try to tie their e-reader to their e-book store, so buying books online for a Nook Color means a default relationship with the Barnes & Noble Nook Book Store.

Most e-readers — whether they offer downloading of e-books or not — are capable of sideloading. E-books may be copied onto memory cards from a computer and accessed on the e-reader. Most offer USB connectivity. Connecting the e-reader to a computer with a USB cable lets you mount the e-reader as an external device or drive, allowing e-books to be dragged and dropped. There are also independent e-book management programs (most notably Calibre), that can be used to manage an e-book library and the contents of an e-reader through sideloading. One thing to keep in mind, though. File format compatibility doesn't go away with sideloading. In other words, sideloading content onto your Kindle doesn't get past the fact that a Kindle can't read EPUB format e-books.


  • When traveling, Internet connectivity (via Wi-Fi or cellular) may not be available in all locations, may be subject to data charges, or may be slow, preventing downloading.
  • Wireless connectivity drains the battery. For example, the Kindle Wi-Fi is rated for 1 month of battery life with wireless off and 3 weeks with wireless on, while the Kindle with 3G active drops from 1 month of battery life to 10 days.
  • For bulk loading of e-books, sideloading is usually much faster than downloading.
  • Sideloading makes it easier to buy e-books from other retailers.


  • Requires a computer, plus USB cable, Bluetooth capable devices or investment in memory cards.
  • Tends to be slightly more complicated and is a less integrated experience than a direct (wireless) e-reader to online e-book account setup.
  • Loses the spontaneity of being able to download a book on a whim from practically anywhere.

Why Sideload If Your E-Reader Is Wireless?

There are several reasons why people with wireless capable e-readers such as the Nook or Kobo might choose sideloading e-books over downloading. The primary reason is that sideloading is the easiest way to access compatible e-books from retailers other than the online e-book store associated with your e-reader. If you own a Nook and would like to buy a compatible EPUB ebook from, you can easily make the purchase through your computer and sideload the title to your Nook. Sideloading also makes it easy to access documents of your own that you may want to take with you and read -a PDF business report, for example. If you have multiple e-readers in your household and don't want everyone to have access to your online e-book store account, sideloading lets you share your e-books (within DRM restrictions) among multiple e-readers.