The alt-right (short for alternative right) is a loose far-right movement and subculture based predominantly on the internet. Although primarily situated in the US, the alt-right is a global movement influencing various political groups in the west.
Who is in the alt-right?
Early online far-right
Although early precedents and intellectual influences can be traced before this point, the alt-right only emerged as a mass movement when it associated itself with imageboard culture. Imageboards, of which 4chan was by far the largest, had before the 2010s been a largely left-libertarian space known for its irreverence for social norms. When a new subcommunity called /new/ was introduced in 2010, dedicated to discussing current news events, this irreverence resulted in a race to the bottom to voice the most heinous political takes possible. Shocked by the virulent racist low-effort trolling, the site administrator deleted the board in early 2011, but months later established a new board /pol/ to take its place. Originally functioning as a "containment board" to separate racist trolling from the rest of the site, this board nevertheless grew to be a large influence on its culture over the following years.
Imageboard culture was popular outside of imageboards, often seen as a trendsetter for new internet memes. The 4chan community would often get immensely frustrated appropriation of their memes by other communities, inspiring a hatred of Reddit, 9gag, and crucially, Tumblr. Tumblr's community had a lot of teenaged girls interested in left-wing social justice activism. Being first-world teenagers, however, this activism would often be rather misdirected, which 4chan posts would then make fun of. This ridicule of Tumblr translated into ridicule of Tumblr's causes, and eventually into reactionary politics, a process encouraged by users from the /pol/ board.
An important case of this evolution took place on the video games board /v/. /v/ had always been strongly opposed to the corporate video games press. When around this period video games journalists increasingly began using Tumblr-like social justice rhetoric, this was seen as yet another affront to /v/'s of the gaming community. Much of this frustration was directed into the reaction to Anita Sarkeesian's 2012 fundraiser for her "Tropes vs. Women in Video Games" video series. This social media outrage involved a misogynistic harassment campaign, which she leveraged in order to gain more support for the project, raising $158,922 rather than the original $8,000 goal.