Copying is the duplication of information, or an artifact, based only on an instance of that information or artifact, and not using the process that originally generated it. With analog forms of information, copying is only possible to a limited degree of accuracy, which depends on the quality of the equipment used, and, if applicable, the skill of the operator. With digital forms of information, perfect copying is not only possible, but is, almost by definition, the norm. Copy and paste is frequently used for information a computer user selects and copies to an area he or she wishes.

Organically, copying of genetic information can take place using DNA replication, which is able to copy and replicate the data with a high degree of accuracy, but mistakes are common, and occur in the form of mutations. However, in the process of DNA repair, many of the mistakes are resolved by checking the copied data against the original data.

Most high-accuracy copying techniques use the principle that there will be only one type of possible interpretation for each reading of data, and only one possible way to write an interpretation of data. For example, in DNA replication, an occurrence of guanine in a DNA sequence can be copied because only cytosine bases can easily attach to it, being its complementary base. Then, the instance of guanine is recorded by taking the derived data, in this case the guanine base, and separating it from the original data. Afterwards, the original guanine occurrence is retrieved by attaching another guanine base to the cytosine again. In order to prevent accidental reading of the wrong data, the intermediary cytosine base in this example, a distinction is made between the 5' end and the 3' end. A cytosine base will usually never be paired with another cytosine base, another adenine base or another thymine base, except under high stress where mistakes will occur.

This principle is applied digitally, such as in hard disks, but in a different form. The magnetised data on the disk consists of 1's and 0's. Unlike DNA, it only has two types of information, rather than four types, however, it still has a polar concept of transfer. In this case, the read-write head acts as an intermediary. A data section reading "1", can only trigger one type of response, and "0" for the other. These responses from reading are converted into an electrical form that gets carried through the circuits. Although this can be later converted and processed for other ways of using the data, which can be modified, if a file were being copied from one hard disk to another, the principle ensures that the data is transferred with high fidelity, because only each type of signal can only trigger one type of data write, in this case a 1 or a 0. This excludes exceptions where the data was written incorrectly or the existing data has been corrupted while on the disk such that no distinction can be made, but usually the hard disk returns the area as unreadable.