Fire OS
Fire OS is a mobile operating system based on the Android Open Source Project and created by Amazon for its Fire tablets, Echo smart speakers and Fire TV devices. It includes proprietary software, a customized user interface primarily centered on content consumption, and heavy ties to content available from Amazon's own storefronts and services. Apps for Fire OS are provided through the Amazon Appstore.

History

Amazon only began referring to the Android derivative as Fire OS with its third iteration of Fire tablets. Unlike previous Fire models, whose operating system is listed as being "based on" Android, the "Fire OS 3.0" operating system is listed as being "compatible with" Android.

Fire OS 5 
which is based on Android 5.1 "Lollipop", added an updated interface. The home screen features a traditional application grid and pages for content types as opposed to the previous carousel interface. It also introduces "On Deck", a function which automatically moves content out of offline storage to maintain storage space for new content, the speed reading tool "Word Runner", and screen color filters. Parental controls were enhanced with a new web browser for FreeTime mode featuring a curated selection of content appropriate for children, as well as "Activity Center" for monitoring usage by children. Fire OS 5 removed support for device encryption; an Amazon spokesperson stated that encryption was an enterprise-oriented feature that was underused. In March 2016, after the removal was publicized and criticized in the wake of the FBI–Apple encryption dispute, Amazon announced that it would be restoring the feature in a future patch.

Fire OS 6 
which is based on Android 7.1.2 "Nougat", its main changes/new additions include:

 Adoptable storage: allows users to format and use their SD card as internal storage,
 Doze/App standby: aim to improve battery life by forcing device to sleep when user is not actively using it. This adds restrictions on Apps that want to do background processing and polling etc.

MediaTek Exploits (2019) 

In early 2019 exploit(s) for 6 Fire Tablet models and 1 Fire TV model were discovered and allowed: gaining temporary root access, permanent root access, bootloader unlocking, these exploit(s) were caused due to security vulnerability(s) in multiple MediaTek chipsets

Fire OS 7 

Which is based on Android 9.0 "Pie" was released in 2019 and is available for all 8th generation and above Fire tablets.

Further History 

In February of 2022 Amazon announced that the Docs app would be replaced by document creation functionality in the Files app in May of 2022.

In February of 2022 Amazon introduced a improved home editing system.

Features
Fire OS uses a customized user interface designed to prominently promote content available through Amazon services, such as Amazon Appstore, Prime Video, Amazon Music & Audible, and Kindle Store. Its home screen features a carousel of recently accessed content and apps, with a "favorites shelf" of pinned apps directly below it. Sections are provided for different types of content, such as apps, games, music, audiobooks, and video among others. A search function allows users to search through their local content library or Amazon's stores. Similarly to Android, sliding from the top of the screen exposes quick settings and notifications. Fire OS also provides integration with Goodreads, Facebook, and Twitter. X-Ray is also integrated into its playback functions, allowing users to access supplemental information on what they are currently viewing. The OS features a user system, along with Kindle FreeTime, a suite of parental controls which allow parents to set time limits for using certain types of content. Another feature is Amazon GameCircle, which is a retired online multiplayer social gaming network released by Amazon. It allowed players to track their achievements and compare their high scores on a leader board. It debuted in July 2012 and was retired September 5, 2018.

Amazon's ecosystem

Fire OS devices comes with Amazon's software and content ecosystems such as Here WeGo with a clone of Google Maps API 1.0. Amazon cannot use the Android trademarks to market the devices. Apps for Fire OS are provided through the Amazon Appstore.

Fire OS devices do not have Google mobile services, including the Google Play Store or proprietary APIs, such as Google Maps or Google Cloud Messaging. Google Play Store can be installed, and third-party apps can still be sideloaded via APK files, although full compatibility is not guaranteed if the app depends on Google services.

Members of the Open Handset Alliance (which include the majority of Android OEMs) are contractually forbidden to produce Android devices based on forks of the OS; therefore, Fire tablets are manufactured by Quanta Computer, which is not an OHA member.

List of Fire OS versions

The releases are categorized by major Fire OS versions based upon a certain Android codebase first and then sorted chronologically.

Fire OS 1 – based on Android 2.3 Gingerbread
 system version = 6.3.1
 system version = 6.3.2 – longer movie rentals, Amazon cloud synchronization
 system version = 6.3.4 – latest version for Kindle Fire (1st Generation) (2011)

Fire OS 2 – based on Android 4.0 Ice Cream Sandwich
 system version = 7.5.1 – latest version for Kindle Fire HD (2nd Generation) (7" 2012)
 system version = 8.5.1 – latest version for Kindle Fire HD 8.9" (2nd Generation) (2012)
 system version = 10.5.1 – latest version for Kindle Fire (2nd Generation) (2012)

Fire OS 2.4 – based on Android 4.0.3(?)

Fire OS 3 Mojito – based on Android 4.1 Jelly Bean
 3.1
 3.2.8 – rollback point for Kindle Fire HDX (2013)
 3.5.0 – introduces support for Fire Phone; Android 4.2.2 codebase
 3.5.1 – Fire Phone maintenance version

Fire OS 4 Sangria – based on Android 4.4 KitKat
 4.1.1
 4.5.5.1
 4.5.5.2
 4.5.5.3 – latest version for some tablets released in 2013, Kindle Fire HDX (3rd Generation), Kindle Fire HDX 8.9" (3rd Generation), Kindle Fire HD (3rd Generation)
 4.5.5.5 – latest version for some tablets released in 2013 (e.g. some Kindle Fire tablets of 3rd Generation)
 4.6.6.0 – Fire Phone
 4.6.6.1 – latest version for the Fire Phone
 4.7.8.4 – Last version for the fire phone (2019)
 4.8.2.9 – Last version for the fire phone (2019)

Fire OS 5 Bellini – based on Android 5.1.1 Lollipop
 5.0
 5.0.5.1 – introduction of Fire TV
 5.0.1
 5.1.1
 5.1.2
 5.1.2.1
 5.1.4
 5.2.1.0 – Fire TV devices
 5.2.1.1 
 5.2.1.2
 5.2.4.0
 5.2.6.0
 5.2.6.1
 5.2.6.2
5.2.8.4
 5.3.1.0
 5.3.1.1 – August 2016
 5.3.2.0 – November 2016
 5.3.2.1 – December 2016
 5.3.3.0 – March 2017
 5.3.6.4 – version for Fire HD 8 (6th Generation)
 5.3.6.8
 5.3.7.0
 5.3.7.1
 5.3.7.2 – for Fire HD 8 & Fire HD 10 (7th Generation)
 5.4.0.0 – June 2017
 5.4.0.1 – August 2017
 5.5.0.0 – November 2017: Only for Fire HD 10 (2017) with hands-free Alexa
 5.6.0.0 – November 2017
 5.6.0.1 – January 2018
 5.6.1.0 – March 2018: version for tablets released in 2014 (e.g. some Fire tablets of 4th Generation)
 5.6.2.0 – July 2018: Hands-Free Alexa For Fire 7 & HD 8 (2017) only
 5.6.2.3 – April 2018: Latest version for first and second generation Fire TV devices
 5.6.3.0 – November 2018: for Fire 7 (5th to 7th Generation); Due to a mistake, this version was accidentally released as 5.3.6.4 on some Fire tablets instead of 5.6.3.0, but includes the same update features.
 5.6.3.8 – April 2019
 5.6.4.0 – May 2019, September 2019: for Fire HD 8
 5.6.6.0 – May 2020
 5.6.7.0 – August 2020
 5.6.8.0 – November 2020: Latest version for Fire (5th Generation), Fire HD 6 (4th Generation), Fire HD 7 (4th Generation), Fire HD 8 (5th and 6th Generation), Fire HDX 8.9 (4th Generation), and Fire HD 10 (5th Generation)
 5.6.9.0 – December 2020: Latest version for Fire (7th Generation), Fire HD 8 (7th Generation), and Fire HD 10 (7th Generation)
 5.8.6.8 – July 2019
 5.8.7.9 – August 2019
 5.7.8.2 – September 2019

Fire OS 6 – based on Android 7.1.2 Nougat
 6.2.1.0 – October 2017, released on third generation Fire TV
 6.2.1.2 – December 2017
 6.2.1.3 – May 2018
 6.3.0.1 – November 2018
 6.3.1.2 – July 2019: version for Fire 7 (9th Generation)
 6.3.1.3 (information needed)
 6.3.1.4 (information needed)
 6.3.1.5 – September 2019: last version of FireOS 6 for Fire HD 8 (8th generation) 
 6.5.3.4 – September 2019: Last version for Fire 7 (7th generation)
 6.5.3.5 – November 2019

Fire OS 7 – based on Android 9.0 Pie
 7.3.1.0 – October 2019: First version for Fire HD 10 (9th Generation)
 7.3.1.1 – October 2019: Second version for Fire HD 10 (9th Generation)
 7.3.1.2 – February 2020: Third version for Fire HD 10 (9th Generation)
 7.3.1.3 – April 2020: Fourth version for Fire HD 10 (9th Generation)
 7.3.1.4 – June 2020: Fifth version for Fire HD 10 (9th Generation)
 7.3.1.5 – August 2020: First version of FireOS 7 for Fire HD 8 (8th Generation)
 7.3.1.6 – October 2020
 7.3.1.7 – November 2020
 7.3.1.8 – February 2021
 7.3.1.9 – May 2021
 7.3.2.1 – September 2021
 7.3.2.2 – November 2021: Latest version for 8th Generation, 9th Generation, 10th Generation and 11th Generation devices

List of Fire OS devices
 Fire Tablets 
 Fire TV
 Fire Phone
 Amazon Echo
 Amazon Echo Show

See also
 Nokia X software platform, a similar fork by Nokia
 Tizen, a Linux-based OS by Samsung Electronics with an optional Android runtime
 Sailfish OS, a Linux-based mobile OS by Jolla which includes an Android runtime
 BlackBerry 10, a QNX-based mobile OS by BlackBerry which includes an Android runtime and comes with the Amazon Appstore preloaded
 Comparison of mobile operating systems

References

External links
 

Amazon (company)
Android (operating system)
Android forks
ARM operating systems
Mobile operating systems
Tablet operating systems