Alt Left is a political label used to describe far-left activists, Antifa groups, and progressive politicians who fall outside the mainstream of liberal politics 2. The term functions both as a self-affirming banner adopted by a small pocket of fringe leftist writers and as a pejorative deployed by conservative pundits and, later, President Donald Trump 2. Vanity Fair and The New Republic both treated the phrase as ill-defined and largely rhetorical rather than a coherent political movement 1.

The New Republic argued that the phrase was legitimized in part by red-baiting liberals who feared the rise of a progressive populist movement, and pointed out that alt-left had always been an insult rather than a self-chosen identity 2. Unlike alt-right, which was coined by white supremacists as branding for their own movement, alt-left was invented from outside the groups it described 2. Vanity Fair's coverage focused on the term's use by contrarian liberal writers who criticized fellow leftists for identity politics and Hollywood grandstanding 1.

The label is typically deployed in one of two ways. Conservative commentators use it to lump progressive Democrats, Antifa activists, and any left-wing protester into a single scary category, often as a rhetorical mirror to the alt-right 2. A small pocket of self-identified alt-left writers, mostly clustered around AltLeft.com and adjacent Facebook communities between 2015 and 2016, used it as an affirmative label for anti-political-correctness leftism 7. Urban Dictionary's top definitions frame the alt-left almost entirely as an insult, describing it as anti-feminist and 'the alt-right wearing anarchist and communist clothing' 5.