The series consists of thirteen games available for multiple platforms, and future titles are planned. Most of the games in the series have been positively received and commercially successful. As of February 2019, the Kingdom Hearts series has shipped more than 30 million copies worldwide. A wide variety of related merchandise has been released along with the games, including soundtracks, figurines, companion books, light novels, cards, and comic series.
Kingdom Hearts is the first game in the series, released in Japan on March 28, 2002 for PlayStation 2. Tetsuya Nomura has served as game director, his first time in this position. Kingdom Hearts introduced the main characters (Sora, Kairi and Riku) of the series, and established the plot's framework involving hearts and dark beings known as the Heartless. It also established the role of Disney characters in the series, with character cameos from the Final Fantasy series. Kingdom Hearts was released in North America on September 17, 2002, and featured additional content that was not in the original Japanese version. The game was later re-released in Japan as Kingdom Hearts Final Mix on December 26, 2002.Final Mix includes the content from the North American release and additional enemies, cutscenes, and weapons.
Kingdom Hearts: Chain of Memories is a direct sequel to the first game. It was released on the Game Boy Advance in Japan on November 11, 2004.Chain of Memories was touted as a bridge between the two PlayStation 2 titles, introducing and previewing plot elements that would be explored in the next game. The gameplay system is a departure from the original and employs card game mechanics in real time. Players construct decks out of cards that correspond to different actions in battle, such as attacking or using magic. It was remade into a PlayStation 2 game titled Kingdom Hearts Re:Chain of Memories, which contains polygonal graphics instead of the sprites used in the original game. The remake was released in Japan as a second disc packaged with Kingdom Hearts II Final Mix on March 29, 2007, and in North America as a standalone title on December 2, 2008.
Kingdom Hearts II takes place one year after the events of Chain of Memories. It was released for the PlayStation 2 in Japan on December 22, 2005. The game further explores the "heart" concept by involving a new group of enemies, the Nobodies, which are the cast-off shells of those who have become Heartless. The gameplay is similar to that of the first Kingdom Hearts game, with the addition of the Reaction Command, which performs context-sensitive actions in battle. Kingdom Hearts II was revised into Kingdom Hearts II Final Mix, which contains more material than the original release, such as additional cutscenes and bosses. Kingdom Hearts II Final Mix was released with Kingdom Hearts Re:Chain of Memories in a collection titled Kingdom Hearts II Final Mix+, which was released in Japan on March 29, 2007.
Kingdom Hearts Coded is an episodic mobile phone game that picks up directly after Kingdom Hearts II. The "preinstall" episode was released in Japan on November 18, 2008 and eight episodes were released between June 3, 2009 and January 28, 2010. The game was remade for the Nintendo DS as Kingdom Hearts Re:coded, and features updated gameplay combining that of two later titles in the series, 358/2 Days and Birth by Sleep. Unlike the original version, Re:coded was released internationally: October 7, 2010 in Japan; January 11, 2011 in North America; and January 14, 2011 in Europe.
Kingdom Hearts 358/2 Days was released for the Nintendo DS in Japan on May 30, 2009. It is primarily set between Kingdom Hearts and Kingdom Hearts II, focusing on Roxas' time in Organization XIII and his motives for leaving. It is the first game in the series to feature cooperative multiplayer in addition to the traditional use of AI-controlled partners. Gameplay is mission-based with optional objectives that yield additional rewards. The game also has a unique panel system which governs character improvement, special abilities, and equipped weapons.
Kingdom Hearts Birth by Sleep is a prequel to the series, released for the PlayStation Portable in Japan on January 9, 2010, and in North America on September 7, 2010 with additional content. The game is set ten years before the events of the first Kingdom Hearts game, revealing the origins of the villain, Xehanort. It consists of four scenarios, three of which focus on one of the game's three protagonists, Terra, Ventus and Aqua. The game was re-released in Japan under the title Kingdom Hearts Birth by Sleep Final Mix on January 20, 2011 with the content from the English versions as well as new features, such as an additional fifth scenario.
Kingdom Hearts 3D: Dream Drop Distance was released on March 29, 2012 in Japan for the Nintendo 3DS. The game focuses on Sora and Riku's Mark of Mastery exam under Yen Sid in anticipation of Xehanort's return and their subsequent conflicts with enemies from their past. In addition to similar systems inherited from Birth by Sleep, this game features "Dream Eaters" which serve as both enemies and allies. Players may collect and breed friendly Dream Eaters and train them to become more powerful. The English edition came out on July 20, 2012 in Europe while it came out on July 31, 2012 for North America.
Kingdom Hearts χ: At Tokyo Game Show 2012, Square Enix announced Kingdom Hearts χ, previously known as Kingdom Hearts for PC Browsers. It is a browser game for PCs, and is only playable in Japan since July 18, 2013. It features cartoon-like 2D models and is a prequel to the series, taking place before the Keyblade War.
Kingdom Hearts: Unchained χ: An international port of Kingdom Hearts χ that was released for Android and iOS devices featuring content from the original game's release while later diverging from it and providing all-new content.Unchained χ was released in Japan on September 3, 2015, in North America on April 7, 2016, and in Europe on June 16, 2016. Later in April 2017, it was rebranded as Kingdom Hearts: Union X.
Kingdom Hearts III: In September 2010, Tetsuya Nomura stated that his team was too busy with other projects such as Final Fantasy XV (known as Final Fantasy Versus XIII at the time) to work on Kingdom Hearts III. He also stated that his team was doing research concerning the high-definition graphics of the game, and depending on the technical requirements of the next generation consoles. On June 10, 2013, at the E3 Sony press conference, after years of rumors and speculations, Nomura introduced a teaser for Kingdom Hearts III, which stated it was in development for the PlayStation 4. It was announced the next day to be in development for the Xbox One as well. In Kingdom Hearts III, the series protagonist Sora embarks on a journey to regain his lost "Power of Waking" while Sora's friends, Riku and King Mickey, search for the Keyblade wielders, Aqua, Terra and Ventus in preparations for their final battle against Xehanort. The game concludes in the "Dark Seeker Saga". The game was released on January 25, 2019 in Japan and was released on January 29, 2019 worldwide.
A Kingdom Hearts game was developed for V CAST, Verizon Wireless's broadband service, and was released on October 1, 2004 in Japan and on February 4, 2005 in the United States. It was one of the launch games for the V CAST services. The game, developed by Superscape and published by Disney Mobile with no involvement from Square Enix, features gameplay akin to the first Kingdom Hearts game, modified for the input method of mobile phones. The game's storyline features Sora struggling to free himself from a nightmare induced by Maleficent's magic.
Kingdom Hearts Mobile is a Kingdom Hearts-themed social game in which players can play mini-games together. Unlike Kingdom Hearts for the V CAST and Kingdom Hearts Coded, this game does not have a storyline and focuses more on socializing. The service operates in conjunction with Kingdom Hearts Coded—new avatar costumes become available after the player completes an episode of Kingdom Hearts Coded. Kingdom Hearts-related media such as wallpapers, ringtones, graphics, and other items can be purchased and downloaded through the service for mobile phones.
Kingdom Hearts VR Experience: Announced in September 2018, Kingdom Hearts VR Experience is a free, 10-minute interactive video "featuring iconic moments [and music] from the Kingdom Hearts games" with the ability to unlock additional content by progressing through the experience. The first part was released in Japan on January 23, 2019, with the second part releasing in early 2019. The first part had initially been scheduled to release on January 18, 2019, after initial release dates of December 25, 2018 for the first part, with the second part releasing on January 18, 2019.
Kingdom Hearts HD 1.5 Remix was released for the PlayStation 3 in Japan on March 14, 2013. The collection includes remastered versions of Kingdom Hearts Final Mix and Re:Chain of Memories, which include gameplay enhancements and trophy support. In addition, a "Theatre Mode" has been added, consisting of high definition cutscenes from Kingdom Hearts 358/2 Days. The collection was released in North America on September 10, 2013 in Australia on September 12, 2013, and in Europe on September 13, 2013.
Kingdom Hearts HD 2.5 Remix: After the announcement of HD 1.5 Remix, Nomura stated that it would be "pretty unnatural" if Kingdom Hearts II did not receive an HD update. In the credits of HD 1.5 Remix, clips of Kingdom Hearts II Final Mix, Kingdom Hearts Birth by Sleep Final Mix and Kingdom Hearts Re:coded were shown, hinting at another collection. On October 14, 2013, the collection was announced for the PlayStation 3, and will include the previously mentioned games, with Re:coded appearing as HD cinematics, similar to 358/2 Days in HD 1.5 Remix. The collection was released in Japan on October 2, 2014, North America on December 2, 2014, Australia on December 4, 2014, and Europe on December 5, 2014.
Kingdom Hearts HD 2.8 Final Chapter Prologue: In the credits of HD 2.5 Remix, clips of Kingdom Hearts 3D: Dream Drop Distance were shown as well as the inclusion of a secret ending related to the game, hinting at a possible additional collection. In September 2015, Square Enix announced Kingdom Hearts HD 2.8 Final Chapter Prologue. The collection features an HD remaster of Dream Drop Distance as well as Kingdom Hearts χ Back Cover, a cinematic telling of the backstory behind the events of Kingdom Hearts χ, and Kingdom Hearts 0.2: Birth by Sleep – A Fragmentary Passage, a new game taking place after the events of the original Birth by Sleep, told from the perspective of Aqua. It was released in Japan on January 12, 2017, and in North America and Europe on January 24, 2017.
The following are repackaged versions of the above collections:
Kingdom Hearts Starter Pack: HD 1.5 + 2.5 Remix: A collector's pack released in Japan includes Kingdom Hearts HD 1.5 Remix and Kingdom Hearts HD 2.5 Remix.
Kingdom Hearts Collector's Pack: HD 1.5 + 2.5 Remix: A collector's pack released in Japan includes Kingdom Hearts HD 1.5 Remix and Kingdom Hearts HD 2.5 Remix, a code to get an Anniversary Set for Kingdom Hearts χ, music, and a booklet with art from the series.
Kingdom Hearts HD 1.5 + 2.5 Remix: In October 2016, Square-Enix announced a single-disc compilation release of Kingdom Hearts HD 1.5 Remix and Kingdom Hearts HD 2.5 Remix for the PlayStation 4. The compilation was released on March 9, 2017 in Japan; March 28, 2017 in North America; and March 31, 2017 in Europe.
Kingdom Hearts: The Story So Far: Announced in early October 2018, this bundle collects the Kingdom Hearts HD 1.5 + 2.5 Remix PlayStation 4 collection and Kingdom Hearts HD 2.8 Final Chapter Prologue. It was released in North America on October 30, 2018 for the PlayStation 4.
Kingdom Hearts: All-In-One-Package: On January 29, 2019, following the release of Kingdom Hearts III, The Story So Far was replaced by this bundle, which contains everything in The Story So Far, with the addition of Kingdom Hearts III. 
Though Kingdom Hearts III was the end of the "Dark Seeker Saga" which revolved around Xehanort, it had been decided where certain characters end up in order to potentially continue their stories in future games.