An e-reader, also called an e-book reader or e-book device, is a mobile electronic device that is designed primarily for the purpose of reading digital e-books and periodicals.
Any device that can display text on a screen may act as an e-reader, but specialized e-reader devices may optimize portability, readability (especially in sunlight), and battery life for this purpose. Their main advantage over printed books is portability: an e-reader is capable of holding thousands of books while weighing less than one.
An e-reader is similar in form factor to a tablet computer. E-readers are a convenient way to read e-books since the battery can last for several weeks, compared to a smartphone or a laptop that usually needs daily battery charging; in addition an e-reader does not have apps that may distract its user from reading.
The main advantages of electronic paper e-readers are better readability of their screens, especially in sunlight, and longer battery life. Commercially sold electronic paper devices are only available in grayscale. The Sony Librie, released in 2004 and the precursor to the Sony Reader, was the first e-reader to use electronic paper. The Ectaco jetBook Color was the first color e-reader on the market, but its muted colors were criticized.
Many e-readers can use the internet through Wi-Fi and the built-in software can provide a link to a digital Open Publication Distribution System (OPDSS) library or an e-book retailer, allowing the user to buy, borrow, and receive digital e-books. An e-reader may also download e-books from a computer or read them from a memory card. However, the use of memory cards is decreasing as most of the 2010s era e-readers lack a card slot.
There have been several generations of dedicated hardware e-readers. The Rocket eBook was the first commercial e-reader and several others were introduced around 1998, but did not gain widespread acceptance. The establishment of the E Ink Corporation in 1997 led to the development of electronic paper, a technology which allows a display screen to reflect light like ordinary paper without the need for a backlight; electronic paper was incorporated first into the Sony Librie that was released in 2004 and Sony Reader in 2006, followed by the Amazon Kindle, a device which, upon its release in 2007, sold out within five and a half hours. The Kindle includes access to the Kindle Store for e-book sales and delivery.