Photo state machines.

A 'photocopier' (also known as a copier or copy machine) is a machine that makes papercopies of documents and other visual images quickly and cheaply. Most current photocopiers use a technology called xerography, a dry process that uses electrostatic charges on a light-sensitive photoreceptor to first attract and then transfer toner particles (a powder) onto paper in the form of an image. 

Heat, pressure or a combination of both is then used to fuse the toner onto the paper. (Copiers can also use other technologies such as ink jet, but xerography is standard for office copying.) Earlier versions included the Gestetner stencil duplicator, invented by David Gestetner in 1881.

Commercial xerographic office photocopying was introduced by Xerox in 1959,and it gradually replaced copies made by Verifax, Photostat, carbon paper, mimeograph machines, and other duplicating machines.

Photocopying is widely used in the business, education, and government sectors. While there have been predictions that photocopiers will eventually become obsolete as information workers increase their use of digital document creation, storage and distribution, and rely less on distributing actual pieces of paper, as of 2015, photocopiers continue to be widely used.

In the 2010s, there is a convergence in some high-end machines between the roles of a photocopier, a fax machine, a scanner, and a computer network-connected printer into a multi-function printer. Lower-end machines that can copy and print in color have increasingly dominated the home-office market as their prices fell steadily through 2017. Higher-end color photocopiers capable of handling heavy duty cycles and large-format printing remain a costlier specialty for print and design shops.


Chester Carlson, the inventor of photocopying, was originally a patent attorney, as well as a part-time researcher and inventor. His job at the patent office in New York required him to make a large number of copies of important papers. Carlson, who was arthritic, found this to be a painful and tedious process. This motivated him to conduct experiments with photo conductivity. Carlson used his kitchen for his "electrophotography" experiments, and, in 1938, he applied for a patent for the process. He made the first photocopy using a zinc plate covered with sulfur. 

In 1949, Xerox Corporation introduced the first xerographic copier called the Model A.xerox became so successful that, in North America, photocopying came to be popularly known as "xeroxing." Xerox has actively fought to prevent "Xerox" from becoming a genericized trademark. While the word "Xerox" has appeared in some dictionaries as a synonym for photocopying, Xerox Corporation typically requests that such entries be modified, and that people not use the term "Xerox" in this way. 

Some devices sold as photocopiers have replaced the drum-based process with inkjetor transfer film technology.

Among the key advantages of photocopiers over earlier copying technologies are their ability:

• to use plain (untreated) office paper,
• to implement duplex (or two-sided) printing,
• Able to scan several pages automatically with an ADF, and
• eventually, to sort and/or staple output.

Colored toner became available in the 1950s, although full-color copiers were not commercially available until 3M released the Color-in-Color copier in 1968, which used a dye sublimation process rather than conventional electrostatic technology.

The first electrostatic color copier was released by Xerox (the 6500) in 1973. Color photocopying is a concern to governments, as it facilitates counterfeiting currency and other documents: for more information, see Counter feiting section.

There is an increasing trend for new photocopiers to adopt digital technology, thus replacing the older analog technology. With digital copying, the copier effectively consists of an integrated scanner and laser printer. This design has several advantages, such as automatic image quality enhancement and the ability to "build jobs" (that is, to scan page images independently of the process of printing them).

A great advantage of digital copier technology is "automatic digital collation." For example, when copying a set of 20 pages 20 times, a digital copier scans each page only once, then uses the stored information to produce 20 sets. In an analog copier, either each page is scanned 20 times (a total of 400 scans), making one set at a time, or 20 separate output trays are used for the 20 sets.

In certain countries, such as Canada, some universities pay royalties from each photocopy made at university copy machines and copy centers to copyright collectives out of the revenues from the photocopying, and these collectives distribute resulting funds to various scholarly publishers.

Some high-quality color printers and copiers steganographically embed their identification code into the printed pages, as fine and almost invisible patterns of yellow dots. Some sources identify Xerox and Canon as companies doing this.The Electronic Frontier Foundation (EFF) has investigated this issue.