Deathcore is a fusion of death metal and metalcore.

Being a broad term it can mean anything from "downtempo" deathcore, melodic deathcore, grindy deathcore, technical deathcore etc.

1991-1992 was most likely the starting year for deathcore. Damonacy's 1991 demo/EP, From Within, featured elements of dissonant metalcore within their Ripping Corpse like sound. The same goes for Cross Fade a year later, with their emphasis on a peculiar, thuggery hardcore esque groove being noticeable on their technical death metal-flavored demo, Ruined. The next one is Lethargy (consisted of soon-to-be members of Mastodon interestingly enough), who were also playing a technical death metal style, but with a much more proto-mathcore derived sound in their demo Lost in This Existence. However, Australian band Damaged (now known as Terrorrust) on the other hand were much more notable: their early material (The Art of Destroying Life and Do Not Spit) are a mixture of death metal, metalcore and NYHC, sounding extremely similar to mid to late '90s deathcore.

Deathcore gained a lot of traction in the mid '90s. Metalcore itself has already flirted with a fair amount of death metal at this point (All Out War, Arkangel, etc.) though there are bands that took this to the limit. During this period militant, vegan straight edge "hardcore" bands went harder and aggressive by embracing death metal in their music, which in the end becoming a major and influential force on deathcore. In the US, vegan straight edge bands like Abnegation, End of One, Upheaval and Day of Suffering were some of the notable bands that actually began mixing a considerable amount of death metal influences in their framework.

Meanwhile in Europe, the Belgian H8000 scene – which is also vegan straight edge – is an entirely different monster. Congress and Liar pretty much changed the scene's landscape by opting a much more technical and hateful sound with low-key death metal influences, but it was Deformity, Legion and Sektor that started exerting it stronger than their predecessors. Other bands in the continent – some of which were inspired by the H8000 scene – such as Reprisal, Jane, Shaft, Ashlar and Crawlspace went to a similar route.

Other bands such as End of One, One Last Sin, Goatamentise and Embodyment also released their material during this period.

By 2004, deathcore bands like All Shall Perish and Cast From Eden started incorporating melodic death metal and melodic metalcore. Overtime this process started to slowly strip many, if not all, their traditional metalcore roots and sound. Often times, these bands are called "AtG-core" because they took so much influence from At The Gates. In the same year, the breakdown-heavy brutal deathcore bands started appearing and quickly became the poster boy for the genre. These bands often have their roots in brutal death metal and to a lesser extent alt metal, rather than metalcore. Bands such as Suffocation, Internal Bleeding, and Dying Fetus being the main influences for much of these bands, like Suicide Silence and Job for a Cowboy.

This caused a noticeable change in sound. No longer was deathcore a metalcore subgenre, but a death metal one; it shares much of its sound with brutal death metal than it does with metalcore. Thus, bands in this era are to be labeled as second wave deathcore.