Custom software (also known as bespoke software or tailor-made software) is software that is specially developed for some specific organization or other user. As such, it can be contrasted with the use of software packages developed for the mass market, such as commercial off-the-shelf (COTS) software, or existing free software.
Since custom software is developed for a single customer it can accommodate that customer's particular preferences and expectations. Custom software may be designed in stage by stage processes, allowing all nuances and possible hidden dangers to be taken into account, including issues which were not mentioned in the specifications. Especially the first phase in the software development process may involve many departments, including marketing, engineering, research and development and general management.
Large companies commonly use custom software for critical functions, including content management, inventory management, customer management, human resource management, or otherwise to fill the gaps present in the existing software packages. Often such software is legacy software, developed before COTS software packages offering the required functionality became available.
Custom software development is often considered expensive compared to off-the-shelf solutions or products. This can be true if one is speaking of typical challenges and typical solutions. However, it is not always true; custom software development by a reputable supplier is often a matter of building a house upon a solid foundation and, if managed properly, it is possible to do this quickly and to a high standard. In many cases, COTS software requires customization to correctly support the buyer's operations. The cost and delay of COTS customization frequently adds up to the expense of developing custom software.