
Key is a Japanese visual novel video game development studio and brand under the publisher VisualArt's. The video games developed by Key are initially published by VisualArt's and released for Windows; consumer ports are published by Interchannel and Prototype. Key released their debut title, Kanon, in 1999, followed by their second title, Air, in 2000. Both Kanon and Air were initially released as adult games, but Key released their third game, Clannad, in 2004 with a rating of approval for all ages. Key's fourth game, Planetarian: The Reverie of a Little Planet, was also released in 2004 with a rating for all ages, and is described as a "kinetic novel" by the development team because of its completely linear storyline.

Air is a Japanese adult visual novel developed by Key and released on September 8, 2000, for Windows PCs. Key later released versions of Air without the erotic content, and the game was ported to the Dreamcast, PlayStation 2, PlayStation Portable, PlayStation Vita and Nintendo Switch. The story follows the life of Yukito Kunisaki, a traveling showman searching for the "girl in the sky". He arrives in a quiet, seaside town where he meets three girls, one of whom is the key to the end of his journey.

Angel Beats! is a Japanese episodic visual novel developed by Key for Windows PCs. The game is based on the 2010 anime television series Angel Beats!, originally conceived by Jun Maeda, and also adapts scenes featured in the anime. The first of planned six volumes, titled Angel Beats! 1st Beat, was released on June 26, 2015, with a rating for all ages. An English version of 1st Beat was announced to be in development. The story takes place in the afterlife and focuses on Otonashi, a boy who lost his memories of his life after dying. He is enrolled into the afterlife school and meets a girl named Yuri who invites him to join the Afterlife Battlefront—an organization she leads which fights against God. The Battlefront fight against the student council president Angel, a girl with supernatural powers.

Clannad is a Japanese visual novel developed by Key and released on April 28, 2004 for Windows. While both of Key's first two previous works, Kanon and Air, had been released first as adult games and then censored for the younger market, Clannad was released with a rating for all ages. It was later ported to the PlayStation 2, PlayStation Portable, Xbox 360, PlayStation 3, PlayStation Vita, PlayStation 4 and Nintendo Switch consoles. An English version for Windows was released on Steam by Sekai Project in 2015.

Harmonia is a Japanese post-apocalyptic visual novel developed by Key, a brand of VisualArt's. It was released on September 23, 2016 for Windows on Steam, and was available in English before its Japanese release on December 29, 2016. The story is set in a world where artificially intelligent, emotional androids called Phiroids were developed before a rapid decline in human civilization. An emotionless young man named Rei with a mechanical right hand is cared for by a girl in a small town as he gradually learns how to express emotions.

Kanon ("Canon") is a Japanese adult visual novel developed by Key and released on June 4, 1999 for Windows PCs. Key later released versions of Kanon without the erotic content, and the game was ported to the Dreamcast, PlayStation 2 and PlayStation Portable. The story follows the life of Yuichi Aizawa, a high school student who returns to a city he last visited seven years prior, and he has little recollection of the events from back then. He meets several girls and slowly regains his lost memories. The gameplay in Kanon follows a branching plot line which offers pre-determined scenarios with courses of interaction, and focuses on the appeal of the five female main characters by the player character. The game once ranked as the second best-selling PC game sold in Japan, and charted in the national top 50 several more times afterwards. Kanon has sold over 300,000 units across several platforms.

Kud Wafter is a Japanese adult visual novel developed by Key, released on June 25, 2010 for Windows. Kud Wafter is Key's eighth game, along with other titles such as Kanon, Air, and Clannad. Key released a version of Kud Wafter without the erotic content, and the game was ported to the PlayStation Portable and PlayStation Vita. The story follows the lives of high school students Riki Naoe and his close friend Kudryavka Noumi as they start to see more of each other in a romantic relationship. The gameplay in Kud Wafter follows a branching plot line which offers pre-determined scenarios with courses of interaction, and focuses on the appeal of the title character Kudryavka, also known as "Kud" for short.

Little Busters! is a Japanese visual novel developed by Key. It was released on July 27, 2007 for Windows PCs and is rated for all ages. Little Busters! is Key's sixth game, along with other titles such as Kanon, Air, and Clannad. An adult version of the game titled Little Busters! Ecstasy was released on July 25, 2008 for Windows, unlike Kanon and Air, which were first released with adult content and then had later versions with such content removed. Ecstasy was later ported to the PlayStation 2, PlayStation Portable, PlayStation Vita, PlayStation 3, and Nintendo Switch with the adult content removed under the title Little Busters! Converted Edition. An English version for Windows was released on Steam in 2017. The story follows a group of childhood friends now attending high school called the Little Busters, as they decide to form a baseball team. Riki, who is diagnosed with narcolepsy, is tasked to recruit more girls in preparation for a baseball game, and he bonds with each of them on account of their internal conflicts. Meanwhile, Rin gets mysterious letters from her cat Lennon to complete various tasks in order to learn the "secret to this world".

Planetarian: The Reverie of a Little Planet is a Japanese post-apocalyptic visual novel developed by Key, a brand of VisualArt's whose previous works include Kanon and Air. It was released over the Internet on November 29, 2004, for Windows, and is rated for all ages. The game was later ported to the PlayStation 2 (PS2), PlayStation Portable and Nintendo Switch, as well as mobile devices. The story centers on a man who comes across a malfunctioning robot in a dead city. The man, known simply as "the junker", stays with this robot for a time and attempts to fix the projector of the planetarium where the story takes place.

Rewrite is a Japanese visual novel developed by Key, a brand of VisualArt's. It was released on June 24, 2011 for Windows PCs and is rated for all ages. Rewrite is Key's ninth game, along with other titles such as Kanon, Air, and Clannad. Key released a fan disc expanding on the game's story titled Rewrite Harvest festa! on July 27, 2012 for Windows. Rewrite was ported to the PlayStation Portable, PlayStation Vita, PlayStation 3 and PlayStation 4, while Harvest festa! was ported to the PlayStation Vita. An English version of Rewrite and Harvest festa! for Windows will be released by Sekai Project. The story follows the life of Kotarou Tennouji, a high school student with superhuman abilities who investigates supernatural mysteries with five girls from his school in the fictional city of Kazamatsuri. This ultimately leads him into the middle of a conflict between familiar summoners and superhumans with the fate of the world at stake.

Summer Pockets is a Japanese visual novel developed by Key, a brand of Visual Arts. It was released on June 29, 2018 for Windows and is rated for all ages. Summer Pockets is Key's 13th game, along with other titles such as Kanon, Air, and Clannad. It has been ported to iOS and Android devices, and the Nintendo Switch. An English version for Windows was released by Visual Arts in 2020. An expanded version of the game titled Summer Pockets Reflection Blue was also released on June 26, 2020 in Japan. The story is set on a fictional island on the Seto Inland Sea and follows the life of Hairi Takahara, a young man who uses the recent death of his grandmother as an excuse to escape to the island after an unpleasant incident. Once there, he gets to know the townsfolk of Torishirojima and multiple girls who are the focus of the story.

Tomoyo After: It's a Wonderful Life is a Japanese adult visual novel developed by Key released on November 25, 2005 for Windows PCs. The game is a spin-off of Key's earlier all ages game Clannad. Key later released versions of Tomoyo After without the erotic content, and the game was ported to the PlayStation 2, PlayStation Portable, Xbox 360, PlayStation 3 and Nintendo Switch under the title Tomoyo After: It's a Wonderful Life CS Edition; CS stands for "consumer software". The story follows the lives of Tomoya Okazaki, a young man who recently graduated from high school, and his close friend Tomoyo Sakagami as they start to see more of each other in a romantic relationship.