Amazon Kindle

Naming and evolution

Founder and CEO of Amazon.com Jeff Bezos commanded his deputies in 2004 to build the world's best e-reader before Amazon's competitors could. In reference to this e-reader, Amazon originally used the codename Fiona.

The Kindle name was devised by branding consultants Michael Cronan and Karin Hibma. Lab126 tasked them to name the product, so Cronan and Hibma suggested Kindle, meaning to light a fire. They felt this was an apt metaphor for reading and intellectual excitement.

Kindle hardware has evolved from the original Kindle introduced in 2007 and the Kindle DX (with its larger screen) introduced in 2009. The range includes devices with a keyboard (Kindle Keyboard), devices with touch-sensitive high resolution and contrast screens (Kindle Paperwhite), a tablet with the Kindle app (Kindle Fire), and a low-priced model with a touch-sensitive screen (Kindle).

Amazon has also introduced Kindle software for use on various devices and platforms, including Microsoft Windows, iOS, BlackBerry, Mac OS X (10.5 or later, Intel processor only), Android, webOS and Windows Phone. Amazon also has a "cloud" reader to allow users to read and purchase Kindle books using a modern web browser at read.amazon.com.

Content for the Kindle can be purchased online and downloaded wirelessly in some countries, using either standard Wi-Fi or Amazon's 3G "Whispernet" network. Whispernet is accessible without any monthly fee or wireless subscription, although fees can be incurred for the delivery of periodicals and other content when roaming internationally beyond the customer's home country. Through a service called "Whispersync," customers can synchronize reading progress, bookmarks, and other information across Kindle hardware and other mobile devices.

First generation

Kindle

Amazon released the Kindle, its first e-reader, on November 19, 2007, for US$399. It sold out in five and a half hours. The device remained out of stock for five months until late April 2008.

The device features a 6 inches (diagonal) 4-level grayscale display, with 250 MB of internal storage, which can hold approximately 200 non-illustrated titles. It also has a speaker and a headphone jack that allows the user to listen to audio files on Kindle. It is the only Kindle with expandable storage, via an SD card slot.

The device's Whispernet feature was co-designed with Qualcomm, and Kindle was the first device to include free US-wide 3G access to download e-books from Amazon's Kindle Store. Amazon did not sell the first generation Kindle outside the US.

Second generation

Kindle 2

On February 10, 2009, Amazon announced the Kindle 2, the second generation Kindle. It became available for purchase on February 23, 2009. The Kindle 2 features a text-to-speech option to read the text aloud, and 2 GB of internal memory of which 1.4 GB is user-accessible. By Amazon's estimates, the Kindle 2 can hold about 1,500 non-illustrated books. Unlike the first generation Kindle, Kindle 2 does not have a slot for SD memory cards. It was slimmer than the original Kindle. The Kindle 2 features a Freescale 532 MHz, ARM-11 90 nm processor, 32 MB main memory, 2 GB flash memory and a 3.7 V 1,530 mAh lithium polymer battery.

To promote the Kindle 2, in February 2009 author Stephen King made UR, his then-new novella, available exclusively through the Kindle Store.

On July 8, 2009, Amazon reduced price of the Kindle 2 from $359 to $299. On October 7, 2009, Amazon further reduced the price to $259. The Kindle 2 had a manufacturing materials cost estimated at $185.49, in 2009 by iSuppli. On October 22, 2009, Amazon stopped selling the original Kindle 2 in favor of the Kindle 2 international version it had introduced earlier that month.

On November 24, 2009, Amazon released a firmware update for the Kindle 2 that it said increased battery life by 85% and introduced native PDF file support.

Kindle 2 international version

On October 7, 2009, Amazon announced an international version of the Kindle 2 with the ability to download new titles in over 100 countries. It became available October 19, 2009. The international Kindle 2 is physically very similar to the US-only model, although it uses a different mobile network standard.

The original Kindle 2 used CDMA2000 for use on the Sprint network. The international version used standard GSM and 3G GSM, enabling it to be used on AT&T's U.S. mobile network and internationally in 100 other countries.

The international version of the Kindle 2 is believed to have a noticeably higher contrast screen, although Amazon does not advertise this. Another review done by Gadget lab, disputes this and actually states that the font appears to be fuzzier than that of the first generation kindle. The review goes on to say that changes to the Kindle 2 have made it tougher to read the smaller font sizes that most books use. Some writers discuss how the font size is at times worse than that of the first-generation Kindle. It appears that whether the Kindle 2 is clearer or fuzzier than the prior model depends on the font size. These issues became moot when Amazon sourced a higher contrast E Ink technology it dubbed "E Ink Pearl" and which it used in its subsequent e-readers until the introduction of "E Ink Carta".

On October 22, 2009, Amazon lowered the price on the international version from $279 to $259 and discontinued the US-only model. On June 21, 2010, hours after Barnes & Noble lowered the price of its Nook, Amazon lowered the price of the Kindle 2 to $189.

Kindle DX

Amazon announced the Kindle DX on May 6, 2009. This device has a larger screen than the standard Kindle and supports PDF files. It has an accelerometer, which enables the user to seamlessly rotate pages between landscape and portrait orientations when the Kindle DX is turned on its side. It is marketed as more suitable for displaying newspaper and textbook content. The device can only connect to Whispernet in the United States. It can be distinguished from the later International version by a serial number starting with "B004".

Kindle DX international version

Since January 19, 2010, the Kindle DX international version has shipped to over 100 countries. The Kindle DX international version is the same as the DX, except it has support for international 3G wireless, and its serial number starts with "B005".

Kindle DX (2nd generation)

On July 1, 2010, Amazon released the Kindle DX Graphite, the 2nd generation of the DX. As well as dropping the price from $489 to $379, the newer Kindle DX has an E Ink display with 50% better contrast ratio (due to E Ink Pearl technology) and comes only in a graphite case color. It is speculated the case color change is to improve contrast ratio perception further, as some users found the prior white casing highlighted that the E Ink background is light gray and not white. Like the Kindle DX, it does not have a Wi-Fi connection. Its serial numbers start with "B009". The DX Graphite (DXG) is a mix of third-generation hardware and second-generation software. The CPU has the same speed as Kindle Keyboard's CPU but is a different revision, but the DXG has only half the system memory, 128MB. Due to these hardware differences, the DXG runs the same firmware as Kindle 2. Therefore, DXG cannot display international fonts, like the Cyrillic, Chinese, or any other non-Latin font and PDF support and the web browser are limited to matching the Kindle 2's features. The Kindle DX was withdrawn from sale in October 2012, but in September 2013 was made available again in the US and internationally, with the 3G data free to access the Kindle Store and Wikipedia. Loading personal documents by USB is free, but sending them via 3G is about $1 per megabyte. Its battery life is about one week with 3G on and two weeks with 3G off. Text-to-Speech and MP3 playback are supported.

Kindle Keyboard

Amazon announced the third generation Kindle, later renamed "Kindle Keyboard", on July 28, 2010. Amazon began accepting pre-orders for the Kindle Keyboard as soon as it was announced and began shipping the devices on August 27, 2010. On August 25, Amazon announced that the Kindle Keyboard was the fastest-selling Kindle ever. While Amazon does not officially add numbers to the end of each Kindle denoting its generation, reviewers, customers and press companies often referred to this Kindle as the "K3" or the "Kindle 3". The Kindle Keyboard had a 6 inches (15 cm) screen with a resolution of 600x800 (167 PPI).

The Kindle Keyboard is available in two versions. One of these, the Kindle Wi-Fi, was initially priced at $139 and connects to the Internet via Wi-Fi networks. The other version called the Kindle 3G, was priced at $189 and includes both 3G and Wi-Fi connectivity. The built-in free 3G connectivity uses the same wireless signals that cell phones use, allowing it to download and purchase content from any location with cell service. The Kindle Keyboard is available in two colors: classic white and graphite. Both versions use a E Ink "Pearl" display, which has a higher contrast than prior displays and a faster refresh rate than prior e-ink displays. However, it remains significantly slower than traditional LCDs. An ad-supported version, the "Kindle with Special Offers" was introduced on May 3, 2011, with a price reduction of $25 less than the no ads version, for $114. On July 13, 2011, Amazon announced that due to a sponsorship agreement with AT&T, the price of the Kindle 3G with ads would be $139, $50 less than the Kindle 3G without ads.

The Kindle Keyboard is 0.5 inches shorter and 0.5 inches narrower than the Kindle 2. It supports additional fonts and international Unicode characters and has a Voice Guide feature with spoken menu navigation. Experimental features include a browser based on the popular WebKit rendering engine (but browser may be limited to 50MB of 3G per month to websites other than Amazon and Wikipedia in territories outside the United States), Text-to-Speech that can read aloud the text from books and other content, and an MP3 player. Internal memory is expanded to 4 GB, with approximately 3 GB available for user content. Battery life is advertised at up to two months of reading half an hour a day with the wireless turned off, which amounts to roughly 30 hours.

Reception

The Kindle Keyboard generally received good reviews after launch. Review Horizon describes the device as offering "the best reading experience in its class" while Engadget states, "In the standalone category, the Kindle is probably the one to beat".

Fourth generation

Kindle 4

Amazon announced the fourth-generation Kindle on September 28, 2011 ($80 ad supported, $110 no ads). Retaining the 6 inch e-ink display of the previous Kindle model as well as Amazon's experimental web-browsing capability with Wi-Fi, the fourth-generation Kindle features a slight reduction in weight and size in a silver-grey bezel, as well as nine hard keys, a cursor pad, an on-screen rather than physical keyboard, a flash storage capacity of 2 GB, and an estimated one month battery life under ideal reading conditions.

Kindle Touch

Amazon announced a touchscreen Kindle, called the Kindle Touch, on September 28, 2011, available with Wi-Fi ($100 ad-supported, $140 no ads) or Wi-Fi/3G connectivity ($150 ad supported, $190 no ads). Via 3G the device is able to connect to the Kindle Store, download books and periodicals, and access Wikipedia. Experimental web browsing (outside Wikipedia) on Kindle Touch 3G is only available over a Wi-Fi connection. (Kindle Keyboard continues without this restriction). The usage of the 3G data is limited to 50MB per month. The device uses the same 6 inch E-ink screen of the previous Kindle model, with the addition of an infrared touch-screen control. Like its predecessor, the Kindle Touch has a capacity of 4 GB and battery life of two months under ideal reading conditions. The Kindle Touch began to ship on November 15, 2011 (U.S. only). Amazon announced in March 2012 that the device would be available in the UK, Germany, France, Spain and Italy on April 27, 2012. The Touch was the first Kindle to support X-Ray, which lists the commonly used character names, locations, themes, or ideas in a book. In January 2013, Amazon released the 5.2.0 firmware that updated the operating system to match the Paperwhite's interface with the Touch's MP3/audiobook capabilities remaining.

Fifth generation

Kindle 5

Amazon announced a new version of the regular Kindle on September 6, 2012. The Kindle 5 was released on September 6, 2012 ($70 ad-supported, $90 no ads). The Kindle has a black bezel, in contrast to the Kindle 4 which was available in silver-grey, and has better contrast. Amazon also claims that it has 15% faster page loads. It has a 167 PPI display and was the lightest Kindle at 5.98 oz until 2016's Kindle Oasis.

Kindle Paperwhite (1st generation)

The Kindle Paperwhite (1st generation) was announced on September 6, 2012, and released on October 1. It has a 6 in, 212 PPI E Ink Pearl display (758×1024 resolution) with four built-in LEDs to illuminate the screen. It was available in Wi-Fi ($120 ad-supported, $140 no ads) and Wi-Fi + 3G ($180 ad-supported, $200 no ads) models, with the ad-supported options only intended to be available in the United States. The light is one of the main features of the Paperwhite and it has a manually adjusted light level. The 3G access restrictions are the same as the Kindle Touch, and usage of the 3G data is limited to 50 MB per month and only on Amazon and Wikipedia's websites; additional data may be purchased. Battery life is advertised as up to eight weeks of reading with half an hour per day with wireless off and constant light usage; this usage equals 28 hours. The official leather cover for the Paperwhite uses the hall effect sensor in the device that detects when the cover is closed/opened to turn the screen off/on respectively. This device was the first Kindle to track one's reading speed to estimate when one will finish a chapter or book; this feature was later included with updates to the other Kindles and Kindle Fire tablets. The Kindle Paperwhite lacks physical buttons for page turning and does not perform auto-hyphenation. Except for the lock screen/power button at its bottom, it relies solely on the touchscreen interface. In November 2012, Amazon released the 5.3.0 update that allowed users to turn off recommended content on the home screen in Grid View (allowing two rows of user content) and included general bug fixes. In March 2014, the Paperwhite 5.4.4 update was released that added Goodreads integration, Kindle FreeTime to restrict usage for children, Cloud Collections for organization and Page Flip for scanning content without losing your place, which closely matched the Paperwhite 2's software features.

The Kindle Paperwhite was released in most major international markets in early 2013, with Japan's version including 4GB of storage, and in China on June 7, 2013; all non-Japan versions have 2GB of storage (1.25GB usable).

Reception

Engadget praised the Paperwhite, giving it a 92 out of 100. The reviewer liked the front-lit display, high contrast, and useful software features, but did not like that it was less comfortable to hold than the Nook, the starting price includes ads, and it had no expandable storage.

Shortly after release, some users complained about the lighting implementation on the Kindle Paperwhite. While not widespread, some users found the lighting to be inconsistent, causing the bottom edge to cast irregular shadows. Also, some users complained that the light can only be dimmed, not turned off completely.

Sixth generation

Kindle Paperwhite (2nd generation)

Amazon announced the Kindle Paperwhite (2nd generation), marketed as the "All-New Kindle Paperwhite" and colloquially referred to as the Paperwhite 2, on September 3, 2013; the Wi-Fi version was released in the US on September 30, 2013 ($120 ad-supported, $140 no ads), and the 3G/Wi-Fi version was released in the US on November 5, 2013 ($190 ad-supported, $210 no ads). The Paperwhite 2 features a higher contrast E Ink Carta display technology, improved LED illumination, 25% faster processor (1 GHz) that allows for faster page turns, and better response to touch input compared to the original Paperwhite. It has the same 6" screen with 212 PPI, bezel and 28-hour battery life as the original Paperwhite. The software features dictionary/Wikipedia/X-Ray look-up, Page Flip that allows the user to skip ahead or back in the text in a pop-up window and go back to the previous page, and Goodreads social integration.

The Paperwhite 2 uses a similar experimental web browser with the same 3G data usage restrictions as previous Kindles; there are no usage restrictions when using Wi-Fi. The official Amazon leather cover for the Paperwhite 2 is the same item as was used for the original Paperwhite. It turns the screen on or off when it is opened or closed.

The Kindle Paperwhite 2 was released in most major international markets by the middle of 2014 and this released model includes 4GB of storage. As of September 2014, the US version of the Paperwhite 2 includes 4GB of storage while the previous Paperwhite 2 version has 2 GB.

Reception

Engadget rated the Paperwhite 2 a 93 out of 100, saying while the "all-new" Paperwhite does not offer many new features compared to the original model, but "an improved frontlight and some software tweaks have made an already great reading experience even better."

Seventh generation

Kindle 7

Amazon announced an upgraded basic Kindle and the Kindle Voyage on September 18, 2014. The Kindle 7 was released on October 2, 2014 ($80 ad-supported, $100 no ads). It is the first basic Kindle to use a touchscreen for navigating within books and to have a 1 GHz CPU. It is the first basic Kindle available in international markets such as India, Japan and China. Amazon claims that a single charge lasts up to a month if used half an hour a day without using Wi-Fi.

Kindle Voyage

The Kindle Voyage was released on October 21, 2014, in the US. It has a 6-inch, 300 ppi E Ink Carta HD display, which was the highest resolution and contrast available in e-readers as of 2014 with six LEDs with an adaptive light sensor that can automatically illuminate the screen depending on the environment. It is available in Wi-Fi ($200 ad-supported, $220 no ads) and Wi-Fi + 3G ($270 ad-supported, $290 no ads) models. Its design features a flush glass screen on the front and the rear has angular, raised plastic edges that house the power button, similar to the Fire HDX. The Voyage uses "PagePress", a navigation system that has sensors on either side of the screen that turns the page when pressed. PagePress may be disabled, but the touchscreen is always active. It has over 3 GB of user storage. Amazon claims it has 6 weeks of battery life if used for 30 minutes per day with wireless disabled and brightness set to 10, which is about 21 hours.

Reception

The Verge gave the Voyage a 9.1 out of 10, saying that "this is the best E Ink e-reader I've used, and it's unquestionably the best that Amazon has ever made. The thing is, it's only marginally better than the fantastic Paperwhite in several ways, and significantly better in none" and with those differences in mind, disliked how it costs $80 more than the Paperwhite.

Engadget gave the Voyage a 94 out of a 100, stating that while it was "easily the best e-reader that Amazon has ever crafted," it was also the priciest at $199.

Kindle Paperwhite (3rd generation)

The Kindle Paperwhite (3rd generation), marketed as the "All-New Kindle Paperwhite" and colloquially referred to as the Paperwhite 3 and Paperwhite 2015, was released on June 30, 2015, in the US. It is available in Wi-Fi ($120 ad-supported, $140 no ads) and Wi-Fi + 3G ($190 ad-supported, $210 no ads) models. It has a 6-inch, 1440×1080, 300 ppi E Ink Carta HD display, which is twice the pixels of the original Paperwhite and has the same touchscreen, four LEDs and size as the previous Paperwhite. It has over 3 GB of user accessible storage. This device improved on the display of PDF files, with the possibility to select text and use some functionalities, such as translation on a PDF's text. Amazon claims it has 6 weeks of battery life if used for 30 minutes per day with wireless off and brightness set to 10, which is about 21 hours.

The Paperwhite 3 is the first e-reader to include the Bookerly font, a new font designed by Amazon and includes updated formatting functions such as hyphenation and improved spacing. The Bookerly font was added to most older models via a firmware update. The official Amazon leather cover for the Paperwhite 3 is the same item as was used with the previous two Paperwhite devices.

In February 2016, the Paperwhite 2, Paperwhite 3, Kindle 7, and Voyage received the 5.7.2 update that included a new home screen layout, an OpenDyslexic font choice, improved book recommendations and a new quick actions menu.

On June 30, 2016, Amazon released a white version of the Paperwhite 3 worldwide; the only thing different about this version is the color of the shell.

In October 2016, Amazon released the Paperwhite 3 "Manga Model" in Japan that has a 33 percent increase to page-turning speed and includes 32GB of storage, which is space for up to 700 manga books. The Manga model launched at 16,280 yen (~$156) for the ad-supported Wi-Fi version or 12,280 yen (~$118) for Prime members.

Reception

The Verge gave the Paperwhite 3 a 9.0 out of 10, saying that "The Kindle Paperwhite is the best e-reader for most people by a wide margin" and liked the high-resolution screen but disliked that there was no adaptive backlight; this is featured on the Kindle Voyage.

Eighth generation

Kindle Oasis

Amazon announced the Kindle Oasis on April 13, 2016, and it was released on April 27, 2016 worldwide. The Kindle Oasis is available in Wi-Fi ($290 ad-supported, $310 no ads) and Wi-Fi + 3G ($360 ad-supported, $380 no ads) models. The Oasis has a 6-inch, 300 ppi E Ink Carta HD display with ten LEDs. Its asymmetrical design features physical page turn buttons on one side and it has an accelerometer so the display can be rotated for one-hand operation with either hand. It has one thicker side that tapers to an edge that is 20% thinner than the Paperwhite. It includes a removable leather battery cover for device protection and increased battery life that is available in either black, walnut (brown) or merlot (red); the cover fits in the tapered edge. The Oasis has 28 hours of battery life if used with the battery cover with Wi-Fi off, however, without the cover, the Oasis battery lasts about seven hours. It has nearly 3 GB of user storage. The Oasis includes the Bookerly (serif) font and it is the first Kindle to include the Amazon Ember (sans-serif) font.

Reception

The Guardian's reviewer praised the Oasis' ease in holding, it weighing next to nothing without the cover attached, its long battery life, excellent screen display, even front lighting, usable page-turn buttons and the luxurious feel of the leather cover, however did not like that it was so expensive, that the battery cover only partially protects the back and it is not waterproof. The reviewer concluded, "...the Paperwhite will likely be all the e-reader most will need, but Oasis is the one you'll want. The Oasis is the Bentley to the Paperwhite’s Golf - both will get the job done, just one is a cut above the other."

The Verge gave the Oasis a 9/10, praising its thinness, its weight without the cover and the ability to read with one hand, but did not like that is so expensive, has no adaptive backlight like the Voyage and it is not waterproof.

Kindle 8

Amazon's upgrade of the standard Kindle was released on June 22, 2016 in both black and white colors ($80 ad-supported, $100 no ads). The Kindle 8 features a new rounded design that is 0.35 inches (9 mm) shorter, 0.16 inches (4 mm) narrower, 0.043 inches (1.1 mm) thinner, and 1.1 ounces (30 g) lighter than the previous Kindle 7, and features double the RAM (512MB) of its predecessor. The Kindle 8 is the first Kindle to use Bluetooth that can support VoiceView screen reader software for the seeing impaired. It has the same screen display as its predecessor, a 167 ppi E Ink Pearl touch-screen display, and Amazon claims it has a four-week battery life that can be fully charged within four hours.

Kindle Fire

Amazon announced Kindle Fire, an Android-based tablet that uses a fork of Android on September 28, 2011. It was released for $199 and has a 7-inch IPS color touchscreen display. This was the first Kindle without an E Ink display. However unlike previously released Kindles, it has no 3G option only Wi-Fi.

Kindle Fire HD

The Kindle Fire HD, announced on September 6, 2012, is the second generation of Amazon's color touchscreen Kindle Fire tablet line. It is available in three form factors, 6 inch, 7 inch and 8.9 inch screen sizes. The Fire HD was sold at cost.

In October 2014, Amazon released its next line of Fire HD tablets, officially removing "Kindle" from the device's name.

Kindle Fire HDX

The Kindle Fire HDX, announced on September 25, 2013, is the third generation of Amazon's Kindle Fire tablet line that initially used Fire OS 3; it was available in 7 inch and 8.9 inch screen sizes.

In the 2014 refresh of the tablet, it was renamed Fire HDX officially removing the name "Kindle" from that device's name.

Kindle cases

With the release of the Kindle Paperwhite in 2012, Amazon released the official "Paperwhite Leather Cover" with a natural leather cover and a plastic back that is form-fitted for the device. The cover closes book-like from the left edge. The cover has a sensor that activates the sleep/wake function when it is closed/opened and the case weighs 5.6 ounces.

With the release of the Kindle Voyage in 2014, Amazon released the official "Protective Cover" with either a polyurethane or a leather cover. The Voyage attaches to the rear of the Protective Cover magnetically and the case's cover folds over the top and the case weighs 4.6 ounces. The case can fold into a stand, propping the Kindle up for hands-free reading.

Kindle audio adapter

In May 2016, Amazon released the official Kindle Audio Adapter for reading e-books aloud via a text-to-speech (TTS) system for the blind and visually impaired. This accessibility accessory, initially supported only for the Paperwhite 3 and Oasis, plugs in the USB port and connects to headphones or speakers. Once connected, the reader uses the Voiceview for Kindle feature to navigate the interface and listen to e-books via TTS. This feature only supports e-books, not audiobooks or music.

Using the accessory reduces the Paperwhite 3's battery life to six hours. As an alternative to the official adapter, a generic USB to audio converter will also work with Voiceview.

Kindle applications

Amazon released the Kindle for PC application in late 2009, available for Microsoft Windows systems. This application allows ebooks from Amazon's store or personal ebooks to be read on a personal computer, with no Kindle device required. Amazon released a Kindle for Mac app for Apple Macintosh & OS X systems in early 2010. In June 2010, Amazon released the Amazon Kindle for Android. Soon after the Android release, versions for the Apple iOS (iPhone and iPad) and BlackBerry OS phones were available. In January 2011, Amazon released Kindle for Windows Phone. In July 2011, Kindle for HP TouchPad (running webOS) was released in the US as a beta version. In August 2011, Amazon released an HTML5-based webapp for supported web browsers called Kindle Cloud Reader. In 2013, Amazon has expressed no interest in releasing a separate application for Linux systems; the Cloud Reader can be used on supported browsers in Linux. As of July 2016, there is no Kindle Linux application.

On April 17, 2014, Samsung announced it would discontinue its own e-book store effective July 1, 2014 and it partnered with Amazon to create the Kindle for Samsung app optimized for Samsung Galaxy devices. The app uses Amazon's e-book store and it includes a service that offers a monthly selection of free e-books.

On June 2016, Amazon started to release the new Page Flip feature to its Kindle applications. This feature allows the user to flip through nine thumbnails of page images at a time.

Kindle sales

Specific Kindle sales numbers are not released by Amazon.com; however, CEO Jeff Bezos stated in a shareholders' meeting in January 2010 that "millions of people now own Kindles". According to anonymous inside sources, over three million Kindles had been sold as of December 2009, while external estimates, as of Q4-2009, place the number at about 1.5 million. According to James McQuivey of Forrester Research, estimates are ranging around four million, as of mid-2010. On March 6, 2011, AT&T stores officially started sales of the Amazon Kindle.

In 2010, Amazon remained the undisputed leader in the e-reader category, accounting for 59% of e-readers shipped, and it gained 14 percentage points in share. According to an International Data Corporation (IDC) study from March 2011, sales for all e-book readers worldwide reached 12.8 million in 2010; 48% of them were Kindles. In the last three months of 2010, Amazon announced that in the United States its e-book sales had surpassed sales of paperback books for the first time.

In January 2011, Amazon announced that digital books were outselling their traditional print counterparts for the first time ever on its site, with an average of 115 Kindle editions being sold for every 100 paperback editions. In December 2011, Amazon announced that customers had purchased "well over" one million Kindles per week since the end of November 2011; this includes all available Kindle models and also the Kindle Fire tablet. IDC estimated that the Kindle Fire sold about 4.7 million units during the fourth quarter of 2011. Pacific Crest estimated that the Kindle Fire models sold six million units during Q4 2012.

Morgan Stanley estimates that Amazon sold $3.57 billion worth of Kindle e-readers and tablets in 2012, $4.5 billion in Kindle device sales in 2013 and $5 billion in Kindle device sales in 2014.

Document availability

Content from Amazon's Kindle Store is encoded in Amazon's proprietary Kindle formats (.azw, .kf8 and .kfx). In addition to published content, Kindle users can also access the Internet using the experimental web browser, which uses NetFront.

Users can use the Kindle Store to access reading material using the Kindle itself or through a web browser to access content and as of July 2016, there are over 4.6 million e-books available at the store. The store features Kindle Unlimited for unlimited access to over one million e-books for a monthly fee.

For US customers traveling abroad, Amazon originally charged a $1.99 fee to download e-books over 3G while overseas, but later removed the fee. Fees remain for wireless 3G delivery of periodical subscriptions and personal documents, while Wi-Fi delivery has no extra charge.

In addition to the Kindle Store, content for the Kindle can be purchased from various independent sources such as Fictionwise and Baen Ebooks. Public domain titles are also obtainable for the Kindle via content providers such as Project Gutenberg, The Internet Archive and the World Public Library. In 2011, the Kindle Store had more than twice as much paid content as its nearest competitor, Barnes & Noble.

Public libraries that offer books via OverDrive, Inc. also loan titles for the Kindle and Kindle reading apps. Books are checked out from the library's own site, which forwards to Amazon for the completion of the checkout process. Amazon then delivers the title to the Kindle for the duration of the loan, though some titles may require transfer via a USB connection to a computer. If the book is later checked out again or purchased, annotations and bookmarks are preserved.

Features

Operating system updates are designed to be received wirelessly and installed automatically during a period in sleep mode in which Wi-Fi is turned on. A user may install firmware updates manually by downloading the firmware for their device and copying the file to the device's root directory. The Kindle operating system uses the Linux kernel with a Java app for reading e-books.

Kindles are charged using either a computer's USB port or an AC adapter. The Kindle also contains experimental features such a basic web browser. Users can play MP3 music in the background, if the user is using a Kindle that supports MP3 playback. Users needing accessibility due to vision can can use an audio adapter to listen any e-book read aloud on supported Kindles or those with trouble reading the text may use the Amazon Ember Bold font for darker text.

File formats

Kindle devices are designed to use Amazon's own e-book formats: AZW, and, in fourth generation and later Kindles, AZW3, also called KF8. Kindles do not support the EPUB file format used by many other e-book readers. Similarly to EPUB, Amazon's file formats are intended for reflowable, richly formatted e-book content and support DRM restrictions, but unlike EPUB, they are proprietary formats. Free software such as the free and open source calibre, Amazon's KindleGen, and the email based Send-to-Kindle service are available to convert e-books into these formats. Kindle devices can also display some generic document formats such as plain text (TXT) and Portable Document Format (PDF) files; however, reflowing is not supported for these file types.

Proprietary formats (AZW, KF8 and KFX)

The first Kindle devices used the AZW e-book format, which is identical to the Mobipocket (MOBI) format for files that are not DRM-restricted.

In late 2011, the Kindle Fire introduced "Kindle Format 8" (KF8), also known as AZW3 file format. AZW3 supports a subset of HTML5 and CSS3 features, while acting as a container for a backwards-compatible MOBI content document.

In August 2015, all the Kindle e-readers released within the previous two years were updated with a new typesetting and layout engine that adds hyphens, kerning and ligatures to the text; e-books that support this engine require the use of the "Kindle Format 10" (KFX) file format. E-books that support the enhanced typesetting format are indicated in the ebook's description.

Format support by device

The first-generation Kindle can read only unprotected Mobipocket files (MOBI, PRC), plain text files (TXT), Topaz format books (TPZ) and Amazon's AZW format.

The Kindle 2 added native PDF capability with the version 2.3 firmware upgrade. The Kindle 1 could not read PDF files, but Amazon provides experimental conversion to the native AZW format, with the caveat that not all PDFs may format correctly. The Kindle 2 added the ability to play the Audible Enhanced (AAX) format. The Kindle 2 can also display HTML files.

The fourth/fifth/seventh generation Kindles, Touch, Paperwhite (1st, 2nd & 3rd generations), Voyage and Oasis can display AZW, AZW3, TXT, PDF, unprotected MOBI, and PRC files natively. HTML, DOC, DOCX, JPEG, GIF, PNG, and BMP are usable through conversion. The Keyboard and Touch can also play Audible Enhanced (AA, AAX) and MP3 files. The seventh generation Kindle, Kindle Paperwhite (2nd & 3rd generations), Voyage and Oasis can display KFX files natively.

Send-to-Kindle service

Amazon offers an email-based service, called Send-to-Kindle, that will convert HTML pages, Microsoft Word (DOC or DOCX) documents, and will also convert GIF, PNG, and BMP graphics to a Kindle-formatted file to the device sent via 3G for $0.15 per MB or via Wi-Fi for free. In addition, this service can send unprotected MOBI files to a user's Kindle. These services can be accessed by all Kindle hardware devices, iOS devices running Kindle app version 2.9 or greater, and Android devices running Kindle app version 3.5 or greater.

Multiple device abilities and organization

An e-book may be downloaded from Amazon to several devices at the same time, as long as the devices are registered to the same Amazon account. A sharing limit typically ranges from one to six devices, depending on an undisclosed number of licenses set by the publisher. When a limit is reached, the user must remove the e-book from some device or unregister a device containing the e-book in order to add the e-book to another device.

The original Kindle and Kindle 2 did not allow the user to organize books into folders. The user could only select what type of content to display on the home screen and whether to organize by author, title, or download date. Kindle software version 2.5 allowed for the organization of books into "Collections" which behave like non-structured tags/labels: a collection can not include other collections, and one book may be added to multiple collections. These collections are normally set and organized on the Kindle itself, one book at a time. The set of all collections of a first Kindle device can be imported to a second Kindle device that is connected to the cloud and is registered to the same user; as the result of this operation, the documents that are on the second device now become organized according to the first device's collections. There is no option to organize by series or series order, as the AZW format does not possess the necessary metadata fields.

Annotations

Users can bookmark, highlight, and search through content. Pages can be bookmarked for reference, and notes can be added to relevant content. While a book is open on the display, menu options allow users to search for synonyms and definitions from the built-in dictionary. The device also remembers the last page read for each book. Pages can be saved as a "clipping", or a text file containing the text of the currently displayed page. All clippings are appended to a single file, which can be downloaded over a USB cable. Due to the TXT format of the clippings file, all formatting (such as bold, italics, bigger fonts for headlines, etc.) is stripped off the original text.

X-Ray

X-Ray is a reference tool that is incorporated in Kindle Touch and later devices, the Fire tablets, the Kindle app for mobile platforms and Fire TV. X-Ray lets users explore in more depth the contents of a book, by accessing pre-loaded files with relevant information, such as the most common characters, locations, themes, or ideas.

Textbook rentals

On July 18, 2011, Amazon began a program that allows college students to rent Kindle textbooks from three different publishers for a fixed period of time.

Collection of user reading data

Kindle devices may report information about their users' reading data that includes the last page read, how long each e-book was opened, annotations, bookmarks, notes, highlights, or similar markings to Amazon. The Kindle stores this information on all Amazon e-books but it is unclear if this data is stored for non-Amazon e-books. There is a lack of e-reader data privacy — Amazon knows the user's identity, what the user is reading, whether the user has finished the book, what page the user is on, how long the user has spent on each page, and which passages the user may have highlighted.

Kindle development kit and active content

On January 21, 2010, Amazon announced the release of its Kindle Development Kit (KDK). It aims to allow developers to build 'active content' for the Kindle, and a beta version was announced with a February 2010 release date. A number of companies have already experimented with delivering active content through the Kindle's bundled browser, and the KDK gives sample code, documentation and a Kindle Simulator together with a new revenue sharing model for developers. The KDK is based on the Java programming language's Personal Basis Profile 1.1.2 (JSR 217) flavor of packaged Java APIs.

As of May 2014 Kindle store offers over 400 items labeled as active content. These items include simple applications and games, including a free set provided by Amazon Digital Services. As of 2014, active content is only available to users with a US billing address.

In October 2014, Amazon announced that the Voyage and future e-readers would not support active content because most users prefer to use apps on their smartphones and tablets, but the Paperwhite first generation and earlier Kindles would continue to support active content.

Kindle Direct Publishing

Concurrently with the release of the first Kindle device, Amazon launched Kindle Direct Publishing, used by authors and publishers to independently publish their books directly to Kindle and Kindle Apps worldwide. Authors can upload documents in several formats for delivery via Whispernet and charge between $0.99 and $200.00 per download.

In a December 5, 2009 interview with The New York Times, Amazon CEO Jeff Bezos revealed that Amazon keeps 65% of the revenue from all e-book sales for the Kindle. The remaining 35% is split between the book author and publisher. After numerous commentators observed that Apple's popular App Store offers 70% of royalties to the publisher, Amazon began a program that offers 70% royalties to Kindle publishers who agree to certain conditions. Some of these conditions, such as the inability to opt out of the lendability feature, have caused some controversy.

Kindle aftermarket

Working Kindles in good condition can be sold, traded, donated or recycled in the aftermarket. Due to some Kindle devices being limited to use as reading device and the hassle of reselling Kindles, some people choose to donate their Kindle to schools, developing countries, literacy organizations, or charities. "The Kindle Classroom Project" promotes reading by distributing donated Kindles to schools in need. Worldreader and 'Develop Africa' ships donated e-readers to schools in developing countries in Africa for educational use. 'Project Hart', a non-profit created in the legacy of Michael S. Hart, will take donations of e-readers that can be refurbished to give to people in need.

Whether in good condition or not, Kindles should not be disposed of in normal waste due to the device's electronic ink components and batteries. Instead, Kindles at the end of their useful life should be recycled. In the United States, Amazon runs their own program, 'Take Back', which allows owners to print out a prepaid shipping label, which can be used to return the device for disposal.

Criticism

On July 17, 2009, Amazon withdrew from sale two Kindle titles by George Orwell, Animal Farm and Nineteen Eighty-Four, refunded the purchase price to those who had bought them, and remotely deleted these titles from purchasers' devices after discovering the publisher lacked rights to publish the titles in question. Notes and annotations for the books made by users on their devices were left in a separate file but "rendered useless" without the content to which they were directly linked. The move prompted outcry and comparisons to Nineteen Eighty-Four itself: in the novel, books, magazines, and newspapers in public archives that contradict the ruling party are either edited long after being published or destroyed outright; the removed materials go "down the memory hole", the nickname for an incinerator chute. Customers and commentators noted the resemblance to the censorship in the novel, and described Amazon's action in Orwellian terms. An Ars Technica writer also argued that the deletion violated the Kindle's Terms of Service, which states in part:

Upon your payment of the applicable fees set by Amazon, Amazon grants you the non-exclusive right to keep a permanent copy of the applicable Digital Content and to view, use and display such Digital Content an unlimited number of times, solely on the Device or as authorized by Amazon as part of the Service and solely for your personal, non-commercial use.

Amazon spokesman Drew Herdener stated that the company is "... changing our systems so that in the future we will not remove books from customers' devices in these circumstances." On July 23, 2009, Amazon CEO Jeff Bezos posted on Amazon's official Kindle forum an apology about the company's handling of the matter. Bezos said the action was "stupid", and that the executives at Amazon "deserve the criticism received".

On July 30, 2009, Justin Gawronski, a Michigan high school senior, and Antoine Bruguier, a California engineer, filed suit against Amazon in the United States District Court for the Western District of Washington. Gawronski argued that Amazon had violated its terms of service by remotely deleting the copy of Nineteen Eighty-Four he had purchased, in the process preventing him from accessing annotations he had written. Bruguier also had his copy deleted without his consent, and found Amazon practiced "deceit" in an email exchange. The complaint, which requested class-action status, asked for both monetary and injunctive relief. The case was settled on September 25, 2009, with Amazon agreeing to pay $150,000 divided between the two plaintiffs, on the understanding that the law firm representing them, Kamber Edelson LLC, "...will donate its portion of that fee to a charitable organization...". The settlement also saw Amazon guaranteeing wider rights to Kindle owners over its e-books:

For copies of Works purchased pursuant to TOS granting "the non-exclusive right to keep a permanent copy" of each purchased Work and to "view, use and display [such Works] an unlimited number of times, solely on the [Devices]... and solely for [the purchasers'] personal, non-commercial use", Amazon will not remotely delete or modify such Works from Devices purchased and being used in the United States unless (a) the user consents to such deletion or modification; (b) the user requests a refund for the Work or otherwise fails to pay for the Work (e.g., if a credit or debit card issuer declines to remit payment); (c) a judicial or regulatory order requires such deletion or modification; or (d) deletion or modification is reasonably necessary to protect the consumer or the operation of a Device or network through which the Device communicates (e.g., to remove harmful code embedded within a copy of a Work downloaded to a Device).

On September 4, 2009, Amazon offered affected users a choice between a restoration of the deleted e-books, an Amazon gift certificate or a check for the amount of $30.

In December 2010, three e-books written by Selena Kitt were removed due to violations of Amazon's publishing guidelines. For what Amazon describes as "a brief period of time", the books were unavailable for redownload by users who had already purchased them. This ability was restored after it was brought to Amazon's attention; however, no remote deletion took place.

In October 2012, Amazon suspended the account of Linn Nygaard and deleted every e-book on her Kindle; Nygaard is a user in Norway who had purchased her Kindle in the UK. Amazon claimed that she had violated their terms of service but did not specify what she had done wrong. After Nygaard contacted the media, Amazon restored her account and purchased books. The event serves to remind Kindle users that even when a user clicks buy, the user only holds a license to view e-books that can be revoked by Amazon at any time for violating the terms of service.

Richard Stallman criticized the Kindle, citing Kindle terms of service which can censor users, which require the user's identification, and that can have a negative effect on independent book distributors; he also cited reported restrictions on Kindle users, as well the ability for Amazon to delete e-books and update software without users' permission.