Donor registration facilitates donor conceived people, sperm donors and egg donors to establish contact with genetic kindred. Registries are mostly used by donor conceived people to find out their genetic heritage and to find half-siblings from the same egg or sperm donor. In some jurisdictions donor registration is compulsory, while in others it is voluntary; but most jurisdictions do not have any registration system.

There are registries of the fertility clinics etc. as well as independent registries.

Fertility clinics etc. keep registries of donors and receivers. The donor number is generally available to the donor as well as the receivers. On the other hand, a donor doesn't generally know which receivers that are linked to his/her donor number, and the receivers don't generally know the true identity behind the donor number.

In the case of non-anonymous donors, the donor conceived people may know the true identity of the donor behind the donor number.

Since clinic registries are often very limited, independent registries may be more efficient in finding genetic kindred.

Some donors are non-anonymous, but most are anonymous, i.e. the donor conceived person doesn't know the true identity of the donor. Still, he/she may get the donor number from the fertility clinic. If that donor had donated before, then other donor conceived people with the same donor number are thus genetic half-siblings. In short, donor registries matches people who type in the same donor number.

Alternatively, if the donor number isn't available, then known donor characteristics, e.g. hair, eye and skin color may be used in matching siblings.

Donors may also register, and therefore, donor registries may also match donors with their genetic children.