Nintendo Direct

A Nintendo Direct is an informative live-stream hosted by Nintendo. Nintendo Direct live streams reveal new information about games, including upcoming games. Nintendo Direct livestreams were the main source of new information for ARMS before the game's release.

Nintendo Direct 4.12.17
A segment in the 2017-04-12 Nintendo Direct focused on ARMS. The segment introduced Biff, detailed the ARM Getter and Team Fight mode, and revealed Min Min and her stage. The official ARMS Twitter account went live immediately after the Direct.
 * (UK Version, Japanese Version)

ARMS Direct 5.17.17
The ARMS Direct on 2017-05-17 focused almost entirely on ARMS, revealing several new ARMS, new stages, various modes, and three characters (Twintelle, Byte & Barq, and Kid Cobra). The ARMS Global Testpunch was also announced during the ARMS Direct and made available for download immediately afterwards.

Nintendo Direct 9.13.17
A 'Headline' in the Direct focused on the then-upcoming update to Version 3.0.0. It re-iterated information from Gamescom 2017 about Lola Pop, formally introduced her ARMS and announced that control-remapping would be introduced alongside her in Version 3.0.0. The update to Version 3.0.0 was announced for release shortly after the presentation concluded.

Nintendo Direct 3.8.18
A Headline called "We're Extending an Invitation to ARMS Fans" in the 2018-03-08 Nintendo Direct. The one minute, 11 second long segment in the direct announced the ARMS US & Canada Online Open as well as another Global Testpunch, it also mentions the Game Developers Conference for ARMS, as well as Splatoon and Splatoon 2