The game was developed and released episodically on the official Bionicle website throughout 2001, launching in January and concluding in December.

It received awards from the marketing industry, and retrospective reviews have highlighted its expansion of the concept of what Lego-related play can be and its popularity among fans of Bionicle.

[6] During the game, the player controls Takua, an adventurous villager on the island of Mata Nui;[7] Takua is also the playable character in Lego Bionicle: Quest for the Toa, which was released in October 2001, and the events of Mata Nui Online Game directly follow the ending of Quest for the Toa.

After visiting his home village of Ta-Koro, Takua ventures to Po-Koro to inform Huki, a friend of Maku, that she is safe.

When he arrives, he finds the village has been struck by a mysterious disease and that Huki, one of the star players of the island's popular sport of Koli, is gravely ill. Takua finds a popular new type of Koli ball, the Comet ball, and takes one to Turaga Onewa, who discovers they are infected and are the source of the disease.

In Ga-Koro, Nokama assigns Takua the role of Chronicler, tasking him with providing a record of the island's major events.

Kongu and Takua fly to the Rahi hive, where the population has been forced into labor and Lewa, the Toa of air, has been placed under the control of Makuta by an infected mask.

However, the military forces of the other villages arrive to reinforce the company and the Toa Kaita defeat the Manas by deactivating their control towers.

According to Peter Mack, the president of Templar Studios, Lego had contacted the team in 1999 to develop material for their upcoming Bionicle line.

In September 2000, Templar pitched the idea of an adventure game similar to Myst (1993) that would be set on the island of Mata Nui.

Because the story of the main heroes of the line - the Toa - was to be told in other outlets, the game utilized and was based around the Tohunga villagers packaged with McDonald's Happy Meals.

[15] Templar referred to these updates internally as "programs"; the game initially featured only the beach area, but expanded to include all villages on the island of Mata Nui and culminate with the Toa's battle with Makuta.

[16] The first episode of Mata Nui Online Game was released in January 2001;[15] the first sets from the Bionicle toy line itself were not launched until May and June 2001.

[18] The development team at Templar Studios, based in the Lower East Side of Manhattan, witnessed the September 11 attacks from their office; the final chapters of the game, including the dialogue for Makuta during his fight with the Toa, were influenced by the event.

[25] Leah Weston, the senior developer of Bionicle.com, said that Lego was "highly pleased" with Templar's work and noted the site had averaged 500,000 views a month.

[27] At the 2011 Massachusetts Institute of Technology (MIT) Media in Transition 7: Unstable Platforms conference, Aaron Smith cited the game's episodic structure as a reason for the success of the Bionicle website, as it kept players returning for additional content.

[4] In a 2005 article for the journal Kritikos, Thorsten Botz-Bornstein noted the game redefined the traditional expectation of Lego play as the "simplest thing in the world".

He cited the confrontation with Makuta, who declares himself incapable of being destroyed as he is "nothing", as an example of the more spatially abstract, postmodern approach that Bionicle took to the concept of play.

[29] In August 2021, Gray Fore of Screen Rant credited the game with introducing the "aesthetic and visual themes" of Mata Nui to a wide audience.