A Digicore (デジコア, Dejikoa), also referred to as a Computer Kernel (電脳核, Den'noukaku), is a program and data (a collection of numbers and symbols composed of binary code), said to be found at the center of a Digimon's body, that controls the entirety of a Digimon, corresponding to their heart and brain, and analogous to their soul. What is perceived as monsters, cyborgs, among other things by the human eye is all down to information from the Digicore. While a program cannot be classified as a Digimon unless it has a Digicore of its own, in the case of ZERO-ARMS: Grani, it is not classified as a Digimon despite possessing a Digicore. As a characteristic of Demon-species Digimon, they possess a Digicore concentrated with mighty powers of darkness called a Darkcore (ダークコア, Dākukoa).
Because it is life-threatening to a Digimon if there are abnormalities in their Digicore, it is covered and protected by things such as their skeleton and skin, although many Undead Digimon have rotted to such an extent that their Digicores are visible. In Mokumon's case, in order to protect its bare Digicore, it conceals it within a lot of smoke generated by the very thing that it is trying to protect, making it unique in that sense. They can also become weapons themselves, capitalizing on their vast amount of information, and are sometimes placed outside the body. Normally, there is one Digicore per body, but there are exceptions such as the Four Holy Beasts and Huanglongmon, who each have twelve orbiting their bodies.
A Digimon can continue to exist long after its body has rotted away so long as its Digicore remains unharmed, but this also means that the Digicore is a point of failure for the Digimon, as the Digimon will immediately cease functioning if they lose their Digicore. When a Digimon reaches the end of its life span, it compresses and converts its own Digicore into a Digitama, leaving behind its data to the next generation.
When two Digimon undergo Jogress Evolution, their Digicores are normally totally fused, resulting in a single new Digimon; when this process is left incomplete, the resulting Digimon maintains its form in a very unstable state. Ultimate Chaosmon, who is both an extremely powerful Ultimate Digimon and an incomplete Jogress, is thus unable to store its Digicores within its body, so they manifest bare.
The size of a Digimon is determined by the amount of data and content embedded in their Digicore, and the size of the texture expressing their body. As such, that data may be subject to being unable to be completely rendered due to technological limitations, especially if it is extraordinary in size. The percentage of a specific element within a Digicore determines what and how certain features are expressed in a Digimon, in addition to their pedigree. In the case of Dramon-type Digimon, those that bear the "-dramon" suffix in their name must possess Dragon-factor data in their Digicore; the higher the percentage of that data, the more the shape of their body becomes a Dragon-type.
In addition to producing immense amounts of energy, Digicores are also capable of generating intense heat, even reaching the point of causing burns, and are susceptible to overheating if a Digimon is overworked.
In response to Program X, several Digimon survived by altering their Digicores. This caused Digimon to be reborn into a form that could take in the X-Program and eventually it came to a point where a program that opposed Program X was installed into the Digicore, thus creating the X-Antibody.
Prototype Digimon that exist from before Digimon were discovered have an outdated Interface on their brow, allowing them to reconfigure the data stored within their Digicores for such experiments and upon receiving the X-Antibody, release the data found at the deepest parts of their Digicore. In some cases, Digimon can manifest from the "daydream of a Digicore" as a result of the Digicore's very own creativity being released through the Interface.
Those that undergo Death-X-Evolution, among the DORU Series in particular, instinctively hunt the Digicores of other Digimon in order to remain active despite being deceased, even to the point of requiring massive Digicores in order to evolve.
The Digicores (souls) of sinners that fall into the Dark Area are cast into the sentient crimson flames "El Evangelio", which impose judgment upon and offer salvation to them. Being a Demon Lord type, Beelzebumon would have been completely eradicated by the flames under normal circumstances, including its own soul. However, having assimilated the X-Antibody into its body, Beelzebumon (X-Antibody) became able to suppress the will of El Evangelio without incurring the wrath of the flames.
The Black Digicore is an artifact that Barbamon uses to enslave Digimon and humans to his will.
In the past, when a large amount of Digital Points opened up in the Digital World, bringing a large amount of Spiral, the Deva and Four Holy Beasts used the power of the Four Holy Beasts' DigiCores to open a distortion to attract all the Spiral into the same place so that they could deal with them all at the same time. Once all the Spiral arrived in the same place, they used the distortion to send them all to the Dark Area which was enough to get rid of all the Sprial for a long period of time.
Before the Four Holy Beasts slumber to restore the balance of the Digital World they give some of their DigiCores to their Deva subordinates so that they could use their power to help defeat the Spiral. Kumbhiramon gives one to Grappu Leomon which allows it to evolve to Heavy Leomon for the first time. Later, Vajramon gives one to Tyilinmon which allows it to evolve to Mitamamon for the first time. Hiiragi Takumi, having learned that the Four Holy Beasts gave the Deva their DigiCores, has Gaioumon attack and nearly kill Sinduramon and takes its DigiCore by force.
Later, when a Digital Point opens up in the Digital World, Caturamon tries to use one of the DigiCores to re-enact their plan from the past, though the other Deva disagree due to the Four Holy Beasts no longer being around to mitigate the damage the distortion would do to the Digital World and Human World as that was the only reason they were able to successfully act out the plan in the first place. Undeterred, Caturamon enlists the help of Ofanimon of the Three Archangels and gives it another DigiCore so that it would get more power to try and mitigate the effects of the distortion. Unable to do so however, the effects of trying to control the distortion instead causes Ofanimon's emotions to go out of control, leading it to Mode Change to Ofanimon: Falldown Mode and try to deal with the problem by destroying the Human World, as that is where the Digital Points supposedly originated from. Realising the error of its ways, Caturamon teams up with the Humans and they are able to distract Falldown Mode long enough for Caturamon to retrieve the DigiCore, returning Ofanimon back its senses. The two then apologise for their actions, realising the other Deva were right after all and that trying to use that same plan again was too dangerous.