Hostyn grew up in Kingston, Ontario,[2] and played games as a hobby during school and began to enter tournaments in 2011, leading to her career as a professional player.

[3][4] Hostyn became prominent in the StarCraft II scene in 2012 when she beat a number of highly ranked professionals at an event in Las Vegas.

[8] In 2014, Polygon named her one of 2014's 50 admirable gaming people, describing her as "one of the few women succeeding at the top level of the StarCraft II pro scene".

[9] Having lost some of her "competitive drive" for StarCraft II, Hostyn switched to playing Dota 2 in February 2015, explaining "If I can be good at both it’ll be something nobody has really done before.

[15] Scarlett was entered in the Guinness Book of Records as "highest career earnings for a female competitive video game player" on October 5, 2016.