Not invented here (NIH) is a stance adopted by social, corporate, or institutional cultures that avoid using or buying already existing products, research, standards, or knowledge because of their external origins and costs.
The reasons for not wanting to use the work of others are varied, but some can include fear of patent infringement, lack of understanding of the foreign work, an unwillingness to acknowledge or value the work of others, jealousy, or forming part of a wider turf war. As a social phenomenon, this philosophy manifests as an unwillingness to adopt an idea or product because it originates from another culture, a form of tribalism.
The term is normally used in a pejorative sense. The opposite predisposition is sometimes called "proudly found elsewhere" (PFE) or "invented elsewhere".
In computing
In programming, it is also common to refer to the "NIH syndrome" as the tendency towards reinventing the wheel (reimplementing something that is already available) based on the belief that in-house developments are inherently better suited, more secure, more controlled, quicker to develop, and incur lower overall cost (including maintenance cost) than using existing implementations.
In some cases, software with the same functionality as an existing one is re-implemented just to allow the use of a different software license. One approach to doing so is clean room design.
Reasoning in favor of the NIH approach includes:
Some specific approaches can reduce these drawbacks: