Jade Harley is one of the first four protagonists of Homestuck, but is fully introduced later in the story then the first three protagonists. Although she is seen chatting via computer program early in the story, she is only introduced fully to the reader several hundreds of pages in. When Homestuck was first released as a serial story, her first appearance was six months after the first installment. Like her friends, she is thirteen years old, and in the easy scheme of youth subcultures, Jade is most easily described as a hippie. Her enthusiastic demeanor and artistic interests placea her into sharp (and amusing) contrast with her more cynical friends, the goth Rose Lalonde and the hipster Dave Strider.
Homestuck's first character, John Egbert, is introduced as a typical suburban kid, and the following two characters, Rose and Dave, have slightly less typical lives, with aspects of the surreal intruding. By the time we meet Jade Harley, Homestuck's science-fiction plot is already in full swing, and she is never given a "normal" background. Jade Harley is raised, essentially parentless, in a high-tech pinnacle laboratory somewhere in the middle of the South Pacific Ocean, where she grows her own food, practices with her rifle, and engages in experimental nuclear physics. Although seemingly spacey and happy, and prone to bouts of narcolepsy and forgetfulness, Jade also knows far more than any of the other characters about the true nature of their world. Much of the comedic impact of Jade comes from her being cheerful to the point of being naive, at the same time as she is often pulling the strings on her friend's actions.
In the mythological framework of Homestuck, Jade is represented by the aspect of Space, which is associated with creativity and growth. Which is in the usual fashion subverted during the story: Jade grows to be one of the most powerful characters in the story, and shows a sinister side. Much of Jade's character development in Homestuck is reconciling her sometimes disingenuous innocence with her increasing levels of power and sophistication in the story.