Copying is the duplication of information or an artifact based 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 the skill of the operator. There is some inevitable generation loss, deterioration and accumulation of "noise" (random small changes) from original to copy when copies are made. This deterioration accumulates with each generation. With digital forms of information, copying is perfect. Copy and paste is frequently used by a computer user when they select and copy an area of text or content.

In visual art, copying the works of the masters is a standard way that students learn to paint and sculpt. Often, artists will use the term after to credit the original artist in the title of the copy (regardless of how similar the two works appear) such as in Vincent van Gogh's "First Steps (after Millet)" and Pablo Picasso's "Luncheon on the Grass, after Manet" (based on Manet's well-known work). In sculpture, copies have often been made using devices such as the pointing machine, the pantograph or, more recently, computer guided router systems that scan a model and can produce it in a variety of materials and in any desired size. Another way of copying three-dimensional works is by lost-wax casting and other forms of molding and casting.

Prior to the invention of the printing press, the only way to obtain a copy of a book was to copy it out by hand (see scrivener). Throughout the Middle Ages, monks copied entire texts as a way of disseminating and preserving literary, philosophical and religious texts.

Offices need more than one copy of a document in a number of situations. They usually need a copy of outgoing correspondence for their records. Sometimes they want to circulate copies of documents they create to several interested parties.

Until the late 18th century, if an office wanted to keep a copy of an outgoing letter, a clerk had to write out the copy by hand. This technology continued to be prevalent through most of the 19th century. For these purposes, offices employed copy clerks, also known as copyists, scribes, and scriveners.

A few alternatives to hand copying were invented between the mid-17th century and the late 18th century, but none had a significant impact on offices. In 1780 James Watt obtained a patent for letter copying presses, which James Watt & Co. produced beginning in that year. Letter copying presses were used by the early 1780s by people like Benjamin Franklin, George Washington, and Thomas Jefferson. In 1785, Jefferson was using both stationary and portable presses made by James Watt & Co.

During the 19th century, a host of competing technologies were introduced to meet office copying needs. The technologies that were most commonly used in 1895 are identified in an 1895 description of the New York Business College's course program: "All important letters or documents are copied in a letter-book or carbon copies [are] made, and instruction is also given in the use of the mimeograph and other labor-saving office devices."

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 corrected by checking the copied data against the original data.