QR code is a type of two-dimensional code which is nowadays in wide use because of its features such as a large data storing capacity, ease of use, reliability and small surface area of the code. The code is made up of black and white squares which are referred to as modules. The modules are arranged so that they create function patterns and an area of code used for data storage. This paper describes the structure of QR code, its characteristics and the processes of code generation and decoding. There are many forms of QR code which differ in size, appearance and purpose. Those were created as a result of the user’s differing needs. Even though QR code has a large storage capacity, there is an ongoing search for new effective ways to improve its capacity. In this paper, ways to increase QR code capacity involving the introduction of color into the code and data compression are described. The paper also briefly reviews the methods for merging pictures into QR code in the purpose of adding visual interest to the code. Finally, the paper deals with other two-dimensional codes similar to QR code, such as Data matrix and Dot code.