Sasscore is a style of Hardcore that emerged out of Post-Hardcore in the late-1990s and early-2000s alongside the growing Screamo scene. The genre was seen as a reaction to the perceived machismo in hardcore at the time, placing itself as an opposing sound to it. Sasscore took heavy influences from numerous sources outside hardcore, such as Dance-Punk, New Wave, and even Disco, and fused this with influences from inside the scene, such as screamo, Grindcore, and Metalcore. The genre was characterized mainly by its flamboyant stylings, particularly its lisp-y, sassy vocal style, hence the name. Lyrical topics can range, but there was a large tendency for a focus on erotic, sexual imagery from the bands. The genre is noted for its "spastic edge", using angular and chaotic guitar parts, danceable rhythms, synthesizers, and the usage of blast beats to create a manic and tumultuous sound.

Earlier bands from the 1990s such as The Nation of Ulysses, Brainiac, and Le Shok were influential in the aesthetic and attitude of the genre, while not being sasscore themselves. It wasn't until the 2000s, with bands like The Blood Brothers, Black Eyes, and The Plot to Blow Up the Eiffel Tower, that the genre truly took shape, with The Blood Brother's 2003 record …Burn, Piano Island, Burn being a benchmark for the genre. Sasscore, while being influenced by dance-punk, was also influential to the dance-punk bands of the time, most notably Death From Above 1979.

As time went on, certain bands, such as The Number Twelve Looks Like You, The Sawtooth Grin, and early Daughters, would take the same attitude, aesthetic, and techniques of the original scene, and generally lose the original post-hardcore roots of the genre, now combining them with notably more extreme forms of hardcore like Mathcore and containing even more influence from grindcore.

As years passed, the interest in sasscore and the number of bands started to decline, but in the late 2010s it started to see a comeback. Some bands from the original scene that had gone on hiatus or broken up reformed, such as An Albatross or The Number Twelve Looks Like You, and bands such as p.s.you'redead, Terrifying Girls' High School, and SeeYouSpaceCowboy would take heavy cues from the style, with SeeYouSpaceCowboy leaning heavily into marketing themselves as such.